Honestly reading through that was a bit painful. The combinations that are mentioned there are mostly correct but not really for the right reasons. So now I'm about to waste most of an hour going through the multiclass options assuming you intend to primarily go down the warlock line rather than have warlock as a dip. I'm also just going to assume you have the various sourcebooks for options.
A universal thing to consider is that ANY caster multiclass should be compared against each other sort of in their own tier. Warlocks are STARVED for spell slots a lot of the time and because of how the warlock works in multiclassing any slots you get from multiclassing are considered separate for scaling and thererfor stack. A cleric 3/warlock x would have 4 1st level slots and 2 2nd level slots plus whatever they have from warlock as an example. Another thing is that being able to get CON save prof is a notable feature for concentration saves, and that any multiclass other than cleric won't give you heavy armor (clerics get it as a class feature rather than just a simple proficiency) so if you want that you have to start as one of them.
Artificer: Really doesn't have anything that helps you warlock in either the base class or any of your archetypes in it, so unless there is a particular infusion you HAVE to have (enhanced arcane focus and mind sharpener are the only ones to come to mind).
Barbarian: This actually does work somewhat but I think the article gets it wrong on how it's so good. Xanathar's guide added a lot of support for pact of the blade invocations which all work well with barbarian as it turns the warlock into a light paladin. Spend your slots on eldritch smites and knock the enemy prone so you have advantage without using reckless attack, and many warlock pacts work nicely since the features aren't blocked by the rage. I'd only dip 3 or 4 into barbarian depending on if you really want the feat, but even just a 1 or 2 level dip can be worthwhile. five into it nets extra attack which is an available invocation so going that deep delays your spell casting progression quite a bit for a possibly redundant feature. Just remember that the barbarian bonus rage damage only works if you are using strength.
Bard: Makes for an interesting supportive choice as a dip. Most warlocks pump their charisma as their primary stat meaning that you get a lot of spare inspirations to pass around. Dipping for level 3 can net you some decent spells and archetype features, but perhaps the best reason to want to is the two expertise you get. Bards are a bit more likely to dip into warlock than the other way around to get eldritch blast for consistent damage.
Clerics: Along with warlocks are generally an amazing choice of a dip for anyone, and this isn't an exception. A one level dip nets you some amazing features for whatever domain you choose. Perhaps shy away from any that scale directly from your WIS though as that will force you to be quite MAD. Being able to cast healing word on downed allies is also quite useful but unneeded if you pick celestial.
Druid: Generally just a worse cleric as a dip for you with one exception. 2+ levels of a dip to get circle of stars. This is specifically for the Dragon form, which makes you fairly unlikely to fail concentration checks unless you are taking a massive amount of damage from a single source. Still not quite amazing but might be better than cleric dip if you intended to do more than a single level in that one. Three levels also nets you some powerful second level spells like pass without trace or spike growth.
Fighter: The main thing that the guide got wrong was that hexblade was a poor choice with it. There IS redundancy but hexblade still gives you CHA for your weapon attacks as well as the curse, not to mention the rest of the fairly good features. Run around in heavy armor + shield + defensive fighting style should cover you AC wise, and action surge lets you double your EB output. I wouldn't bother dipping more than 2 levels since most of the archetypes can't help at all with spell casting. Two that DO are battlemaster thanks to Tasha's since it got a bunch of maneuvers that work outside of combat, and eldritch knight for things like shield spell access. EB scaling will probably be better than anything you can do with your weapons without significant investment but at that point play pact of the blade and take a better dip for it.
Monk: Basically no redeeming factors to it as a dip because of how the class scales and MADness. Actually worse than artificer in this regard since that can at least make useful infusions.
Paladin: Classic combination that got even better thanks to the hexblade. If you intend to play into tier 3 I'd be tempted to say this is THE best build (maybe with a sorc dip). Just a 2 level dip (starting in paladin) can get you heavy armor, shield+weapon proficiencies, some extra spell slots, and access to the feature divine smite. Going 6 levels in will net you the mighty aura of protection letting you add your charisma bonus to ALL your saves plus your nearby friends. Hexblade lets you use your charisma for weapons, making strength only useful if you care about the heavy armor movement penalty and so possibly dumpable. On top of that, if you progress down warlock you can get the eldritch smite invocation which can STACK with the paladin's letting you double smite on a hit (or triple if you also used a spell).
Ranger: If you took the fighter, rogue, and the druid and removed anything to make you want to take them as dips you get the ranger. So redundant and MAD it's pointless to consider over other options.
Rogue: While it doesn't help much on damage it can help on everything else. Sneak attack is mostly worthless but expertise exists to make you amazing at specific skill checks. Cunning action lets you use a bonus action that some warlock patrons don't give you much to use it on. Archetype choices you have a few good options like the swashbuckler, soulknife, scout, or inquisitive. Inquisitive is a bit of a MAD choice but helps if you are building a party face who can discern the lies of others while also lying to them. Scout helps to let you dodge the issue of disadvantage for making ranged attacks adjacent to enemies. Soul knife basically lets you bardic inspiration yourself on your skill checks to make you a better skill monkey. Swashbuckler is a decent choice because it lets you add your primary stat of CHA to your initiative.
Sorcerer: Like the fighter they got a few things right about it but also messed up and missed other reasons this is considered so good. Personal opinion I think most of the origin options suck for dips and shouldn't be the reason you pick sorcerer. The things that are worth considering is some broken cheese, certain spell selections warlocks normally can't get, and the metamagics. Starting with metamagics as the article mentioned, Quickened spell can let you spend the bonus action to double your EBs (Technically not as good as action surge but you can do it multiple times and they stack to triple your EBs). Distant spell also enables some frankly silly range with EB invocations and the spell sniper feat (1200 ft range). Subtle spell is also a personal favourite for certain spells and helps ignore some ways people shut down casters. Spell selection that warlock doesn't have is mostly just the shield spell but it is so good for improving your survivability that it bears specific mention. The broken cheese is that spell slot creation using sorcery points only go away on long rest and not short, meaning that if you only short rested to regain your warlock slots and then through sorcery points converted them to sorcerer slots (since they are tracked separately) you could generate a lot of extra slots that are low level that you can use for shield castings.
Wizard: No fancy features like metamagic, this dip stands on only it's tradition choices and spell selection for dips. The useful spell selection part is basically only overlap with sorcerer and can't justify tangling with being MAD. There are three possible traditions I can see as justifiable choices. Bladesinger is less useful because of MAD but bonus AC, movement, and saves is tempting enough to consider it an option. Divination for portent cheese, enough said. War magic's two 2nd level features are both useful, since EB spamming doesn't care about the reaction's downsides, and a minor bonus to initiative is appreciable.
This has been my TED talk, thank you for coming and remember that multiclassing is scary but there is almost never a completely "wrong" choice in 5e, only that you could have picked better. Also just be sure to communicate with your GM about how ok they are with any of these concepts, because it's the nice thing to do.
EDIT: I just realized I nearly doubled the length of the article, not sure if that is an oops or a win.
I'm looking for cool multiclasses for the Warlock. I found these but I was curious about the community's opinion!
Honestly reading through that was a bit painful. The combinations that are mentioned there are mostly correct but not really for the right reasons. So now I'm about to waste most of an hour going through the multiclass options assuming you intend to primarily go down the warlock line rather than have warlock as a dip. I'm also just going to assume you have the various sourcebooks for options.
A universal thing to consider is that ANY caster multiclass should be compared against each other sort of in their own tier. Warlocks are STARVED for spell slots a lot of the time and because of how the warlock works in multiclassing any slots you get from multiclassing are considered separate for scaling and thererfor stack. A cleric 3/warlock x would have 4 1st level slots and 2 2nd level slots plus whatever they have from warlock as an example. Another thing is that being able to get CON save prof is a notable feature for concentration saves, and that any multiclass other than cleric won't give you heavy armor (clerics get it as a class feature rather than just a simple proficiency) so if you want that you have to start as one of them.
Artificer: Really doesn't have anything that helps you warlock in either the base class or any of your archetypes in it, so unless there is a particular infusion you HAVE to have (enhanced arcane focus and mind sharpener are the only ones to come to mind).
Barbarian: This actually does work somewhat but I think the article gets it wrong on how it's so good. Xanathar's guide added a lot of support for pact of the blade invocations which all work well with barbarian as it turns the warlock into a light paladin. Spend your slots on eldritch smites and knock the enemy prone so you have advantage without using reckless attack, and many warlock pacts work nicely since the features aren't blocked by the rage. I'd only dip 3 or 4 into barbarian depending on if you really want the feat, but even just a 1 or 2 level dip can be worthwhile. five into it nets extra attack which is an available invocation so going that deep delays your spell casting progression quite a bit for a possibly redundant feature. Just remember that the barbarian bonus rage damage only works if you are using strength.
Bard: Makes for an interesting supportive choice as a dip. Most warlocks pump their charisma as their primary stat meaning that you get a lot of spare inspirations to pass around. Dipping for level 3 can net you some decent spells and archetype features, but perhaps the best reason to want to is the two expertise you get. Bards are a bit more likely to dip into warlock than the other way around to get eldritch blast for consistent damage.
Clerics: Along with warlocks are generally an amazing choice of a dip for anyone, and this isn't an exception. A one level dip nets you some amazing features for whatever domain you choose. Perhaps shy away from any that scale directly from your WIS though as that will force you to be quite MAD. Being able to cast healing word on downed allies is also quite useful but unneeded if you pick celestial.
Druid: Generally just a worse cleric as a dip for you with one exception. 2+ levels of a dip to get circle of stars. This is specifically for the Dragon form, which makes you fairly unlikely to fail concentration checks unless you are taking a massive amount of damage from a single source. Still not quite amazing but might be better than cleric dip if you intended to do more than a single level in that one. Three levels also nets you some powerful second level spells like pass without trace or spike growth.
Fighter: The main thing that the guide got wrong was that hexblade was a poor choice with it. There IS redundancy but hexblade still gives you CHA for your weapon attacks as well as the curse, not to mention the rest of the fairly good features. Run around in heavy armor + shield + defensive fighting style should cover you AC wise, and action surge lets you double your EB output. I wouldn't bother dipping more than 2 levels since most of the archetypes can't help at all with spell casting. Two that DO are battlemaster thanks to Tasha's since it got a bunch of maneuvers that work outside of combat, and eldritch knight for things like shield spell access. EB scaling will probably be better than anything you can do with your weapons without significant investment but at that point play pact of the blade and take a better dip for it.
Monk: Basically no redeeming factors to it as a dip because of how the class scales and MADness. Actually worse than artificer in this regard since that can at least make useful infusions.
Paladin: Classic combination that got even better thanks to the hexblade. If you intend to play into tier 3 I'd be tempted to say this is THE best build (maybe with a sorc dip). Just a 2 level dip (starting in paladin) can get you heavy armor, shield+weapon proficiencies, some extra spell slots, and access to the feature divine smite. Going 6 levels in will net you the mighty aura of protection letting you add your charisma bonus to ALL your saves plus your nearby friends. Hexblade lets you use your charisma for weapons, making strength only useful if you care about the heavy armor movement penalty and so possibly dumpable. On top of that, if you progress down warlock you can get the eldritch smite invocation which can STACK with the paladin's letting you double smite on a hit (or triple if you also used a spell).
Ranger: If you took the fighter, rogue, and the druid and removed anything to make you want to take them as dips you get the ranger. So redundant and MAD it's pointless to consider over other options.
Rogue: While it doesn't help much on damage it can help on everything else. Sneak attack is mostly worthless but expertise exists to make you amazing at specific skill checks. Cunning action lets you use a bonus action that some warlock patrons don't give you much to use it on. Archetype choices you have a few good options like the swashbuckler, soulknife, scout, or inquisitive. Inquisitive is a bit of a MAD choice but helps if you are building a party face who can discern the lies of others while also lying to them. Scout helps to let you dodge the issue of disadvantage for making ranged attacks adjacent to enemies. Soul knife basically lets you bardic inspiration yourself on your skill checks to make you a better skill monkey. Swashbuckler is a decent choice because it lets you add your primary stat of CHA to your initiative.
Sorcerer: Like the fighter they got a few things right about it but also messed up and missed other reasons this is considered so good. Personal opinion I think most of the origin options suck for dips and shouldn't be the reason you pick sorcerer. The things that are worth considering is some broken cheese, certain spell selections warlocks normally can't get, and the metamagics. Starting with metamagics as the article mentioned, Quickened spell can let you spend the bonus action to double your EBs (Technically not as good as action surge but you can do it multiple times and they stack to triple your EBs). Distant spell also enables some frankly silly range with EB invocations and the spell sniper feat (1200 ft range). Subtle spell is also a personal favourite for certain spells and helps ignore some ways people shut down casters. Spell selection that warlock doesn't have is mostly just the shield spell but it is so good for improving your survivability that it bears specific mention. The broken cheese is that spell slot creation using sorcery points only go away on long rest and not short, meaning that if you only short rested to regain your warlock slots and then through sorcery points converted them to sorcerer slots (since they are tracked separately) you could generate a lot of extra slots that are low level that you can use for shield castings.
Wizard: No fancy features like metamagic, this dip stands on only it's tradition choices and spell selection for dips. The useful spell selection part is basically only overlap with sorcerer and can't justify tangling with being MAD. There are three possible traditions I can see as justifiable choices. Bladesinger is less useful because of MAD but bonus AC, movement, and saves is tempting enough to consider it an option. Divination for portent cheese, enough said. War magic's two 2nd level features are both useful, since EB spamming doesn't care about the reaction's downsides, and a minor bonus to initiative is appreciable.
This has been my TED talk, thank you for coming and remember that multiclassing is scary but there is almost never a completely "wrong" choice in 5e, only that you could have picked better. Also just be sure to communicate with your GM about how ok they are with any of these concepts, because it's the nice thing to do.
EDIT: I just realized I nearly doubled the length of the article, not sure if that is an oops or a win.