Im wondering what class people prefer for a classic sort of potion and sorcery kind of witch. I ask because no class seems to perfectly fit, but several arguably have elements of it (magic, potions, otherworldly powers, not strictly academic, etc.)

I think Cleric and Druid actually have a lot more meat to them for this than Warlock. Paladin might also have an interesting potential for a broom wielding witch. 

Land Druid, Tomelock or Chainlock, or really any wizard are fine for this.

I really like the spirit Bard for a witch. You can use a skull as your spell focus.

Artificer alchemist. Pick hexblood if you want to really lean into the classy witchy vibe.

I like it too

Any spellcaster could work. If you're going for a classic occult fairytale witch, I would go Warlock. For a hedge witch, Druid is a good option. And as Comrade_Jenkins said, an Artificer could work pretty well. Cleric would work decently as a "communing with the spirits" witch.

If your DM allows multiclassing, you could even go with a Wizard/Artificer, or replace the Wizard with Warlock if your Charisma is decent (or if your DM allows Warlocks to use Intelligence instead of Charisma)

I think Warlock or Artificer would work best.

Warlock works. Blood Hunter kinda works.

Personally, I think that Witch should get its own class though.

Warlock is great option

Druid would be good for hags and witches that shapeshift for obvious reasons. Warlock is good for the hags that consort with dark forces, probably pact of the tome or chain. The bubbling brew weird sister type witch would be best as a Alchemist, maybe multiclass into a wizard too. For a witch like Circe, a sorcerer should work, as long as they get polymorph spells, I ain't checkin' right now. 

I know you didn't ask for race, but Hexblood is the obvious best choice. A variant human with the ritual caster feet works well too.  

Druid is probably the best Choice for a nature themed witch. Warlock is probably my go to choice for a classic witch though. Pick tons of Debuff spells and curse your opponents. Fun for the whole family! And ask your DM for a broom of flying and you’ll be set.

As The_Summoning_Dark said, hexblood is obvious choice, though I think tiefling might work good as well.

Keep in mind in D&D hags are already a kind of creature; mostly Fey with one Fiend variant due to having relocated to the Lower Planes, I believe, and all pretty vicious and predatory. So that word would have some different connotations in a typical D&D setting than it does for us.

Really, "witch" is more an aesthetic than anything else. Lean into mysticism and occultism over treating magic as a hard science, be a bit asocial, wear lots of ragged and dark clothes. It's mostly Headology when you get down to it.

If you are in a party of witches with classes mentioned already being taken, I think there is a good case for wizard to differentiate themselves thematically as the witch with the most talent and raw magical power, at least at the highest levels. Before that, I guess they can be the extra nerdy one with a snobbish attitude in regards to magic.
"Ugh! Why are you using THAT spell? THIS spell is obviously so much better! Oh, that is right, you do not know how to cast it. Touche."
"You call this a scroll!? It is just chickenscratch and gibberish! And you sell this to the public? How the hell am I supposed to copy it into my spellbook!?"
"You are not pronouncing the spell right, and you need to wave your hands like so. What is wrong with magical education these days? Obviously, whoever taught you absolutely failed, so be thankful that I am here."
"Miss life cleric, I love you and you are one of my bestest bestie, but can you be like that arcana cleric over there and cast prestidigitation on your outfit every once in a while? Like every morning before you head out and every night before you go to bed? There is a mud stain on the underside of your right shoe, and it kills me to see you present yourself like a slob at the temple today. You know what? Here, just let me do it for you."
"Miss shepherd druid! Good to see you, queen! Gyah! You are soooooo cute as a cat! Can I whisper in your ear for a quick second? Can you tell some of your druid friends to... oh, I don't know... transform into a cat and lick their behinds or something before we go in the restaurant? Your doggo friend have dingleberries hanging!"
"My dearest lord sir! I mean no disrespect, but this is not a palace. This is a DUMP. Do you see that disgusting cobweb up there in the chandelier above the dining table, and those nasty dusty spots on top of the books at the top shelves of the library? Your maids missed it. Where is your court wizard? Why do you not have one? Go get one or train one! Why do I always have to be the one to cast dozens of Unseen Servants to clean everyone else's crap up? I slay dragons, tame monsters, and bring gods to their knees to kiss my feet. Lords these days are seriously no better than peasants who do not know how to wipe their own ass! Prince in shining armor my ass!"

I'd love to see the witch have its own class but that seems unlikely to ever happen in the official rules.  Warlock is probably my favorite flavor-wise, but druid and wizard feel almost as "right" to me depending on subclass taken.

This has been out for some time and new subclass options are available now but I have always found this article and the related video a good starting ground when thinking about different witch archetypes:

https://www.flutesloot.com/5e-guide-to-playing-a-witch/ 

I might suggest an Aberrant Mind Sorcerer with the Hexblood lineage. 

If you are looking for a classic witch then warlock, because historically, witches would have been viewed as serving the Devil, so having a character with some sort of patron makes sense.

I probably would multi class as I would take low level Druid for wildshape like cat and crow for flavour but then nature cleric for better spell casting. I wouldn’t want high cr wildshape a like bear. Or a wildfire Druid so the emphasis is on the familiar rather than the character wildshaping.