I know this is probably very niche but does anyone play beyond level 20?  The current rules cater for it I think by allowing you to get additional epic boons rather than a character level having achieved a total of 20 character levels.  The older versions of the game allowed you to get a few levels of this and that and continue indefinitely with your final class (eg. you could be a 3rd level fighter before becoming a 21st level wizard).  It just gives me the irrits knowing that if I take a couple of levels of something I can never reach the potential of ones ultimate class (theoretical as it mostly is 😉).

After 20 it's not so much about leveling up even more, but perhaps working on finishing the campaign and killing a god or three.

I've discussed with my DM that I am interested in playing that far ahead because you still want to do a few sessions with some new toys that you get. I don't know what everyone gets at level 20 (Some quick googling tells me a rogue can convert a miss into a hit or turn any roll into a 20, both things are nuts) so it's really not about continuing into levels but killing some tough enemies, getting some powerful artifacts, and using those to kill another powerful enemy until the campaign itself is properly done.

According to almost every bit of market research WotC have done most people don't play beyond about 12th level, never mind beyond 20th. I'm sure there's a few groups out there doing it but as you say it's very niche 

I have played at a few 2014 5E tables that went to 30.  Their rule was start leveling up in another class that was related or that you had story reasons to pick. A wizard who became very pious during their adventure could start taking Cleric levels or Artificer levels. Cleric because of story behavior, and Artificer because of casting stat.
A few picked up a second subclass but could only advance to 10 in it, but you had to clear it with the DM.

My current table is still debating how to go about higher than 20 in the 2024 rules.

I doubt most people even reach 20 to begin with.

Hitting 20 is ridiculously hard as it is. However, the official setup for doing it is less than satisfying, by the looks of it, and there's very little support for the DM either - the CR system stops being broken and doesn't even try anymore.

What I expect is that the vast majority of campaigns that do make it to L20 will aim to have a handful of quests to resolve the arcs and allow a few chances to play with capstone abilities, then call it a day. They don't use Epic Boons. The remainder may well do so, but I imagine they die out quickly.

As for wanting the capstone, speak to the DM. They may be willing to allow you to continue gaining levels like that. Personally, by the time you get there, I'd just be shoving monsters at you and probably wouldn't be really enjoying it...so they may just turn around and say that's just the consequence multiclassing, we're starting again at L1.

I don't play beyond level 20, or even near it for most games.

I just finished DMing a campaign where we played past level 20 for a half a year or so of weekly sessions. 

Based on this experience, I think Wizards is right not to allow class levels to continue after a maximum of level 20.  Not receiving a level 20 class feature is a fair exchange for having multi classed the entire rest of the campaign, particularly since a lot of multi classes exist to exploit some feature (sorclock sorcery point recovery; having action surge, etc.).  Allowing a player to continue to level up their class at this point basically undoes their decision making up to that point in the game - telling them “that opportunity cost you paid for a boon? You do not have to pay it anymore.”

I also do not think it is a coincidence that a significant number of level 20 class features are kind of “meh.” It ensures the decision of multi classing and foregoing these theoretical capstones (many players will never reach) is a real choice, and one that feels like a fair power exchange.

My campaigns tend to run until level 15. I've known two DMs who have tried to take their campaigns to level 20. The first only made it to level 12 before players started dropping out from boredom and the campaign officially disbanded at level 14. The second is trying currently, but we're only 7th level at this time. Both used published materials (adventures/adventure paths), and the one that got the closest became just one insane fight after another - and everyone got bored.

As cool as it sounds to play a demi-god, for the vast majority of folks it simply is not fun. Encounters at that level are nearly impossible to balance, and there's only so many times a single character can wipe out an entire army of minions before it gets boring (and harder and harder to explain where the baddies keep getting more). Roleplaying usually falls to the wayside and the answer to everything becomes "nuke it". I describe fights above 15th level as fights in which everyone carries nuclear hand grenades. Tactics no longer matter, it just comes down to who is immune to what.

I'm currently playing in my first campaign to level 2 and agree the balancing is awful, even running it as written. The combats are either wiping out 3/4 of the party in a single attack or we're wiping out the enemies at a similar rate and it totally depends on how well we do in initiative. I'm also currently running a campaign that's at level 13 and I'd like to get to 20 but the milestones that look sensible for the rest of the story will only take it to 17 or 18 and I'm already finding it increasingly difficult to make combat interesting  

Quote from HarmAssassin >>

As cool as it sounds to play a demi-god, for the vast majority of folks it simply is not fun. Encounters at that level are nearly impossible to balance, and there's only so many times a single character can wipe out an entire army of minions before it gets boring (and harder and harder to explain where the baddies keep getting more). Roleplaying usually falls to the wayside and the answer to everything becomes "nuke it". I describe fights above 15th level as fights in which everyone carries nuclear hand grenades. Tactics no longer matter, it just comes down to who is immune to what.

Everything about this is a DM problem, not a level 20 problem, though it is a problem exacerbated by Wizards’ lack of guidance on how to run high level campaigns. 

High level combat absolutely can be interesting - it just needs to be designed for high level play.  Mechanics that are more like puzzles; threats that must be stopped in unique ways; pressing matters where players have to make both tactical and strategic choices.  Frankly, this is my favorite tier of combat - every choice matters, and the stakes for success or failure tend to be at their highest.

Roleplay absolutely does not need to fall off either - and that sounds like a DM who is bored of the campaign and out of ideas.  Level 20 roleplay is some of the most fun in the game - at that point, your characters are making decisions for entire kingdoms; they’re the ones interfacing with the leadership of entire nations and giving guidance on choices that can change the lives of countless individuals.  This is the point where the gods themselves might confer with players; where potentially years of relationship building with NPCs have a payoff.

Your post is a generally accepted conjecture - but it is absolutely built upon myths bred of individuals who have never played at the epic tiers or who only have bad experiences due to DMs who ran epic tier games incorrectly.  Posts like this are exactly why Wizards needs to support high level play better - and provide actual guidance on how to run high level games.  As it stands, fiction and limited experience defines the narrative of how epic games turn out; not actual experience.

As another aside, I also think part of the problem is that many people think they are designing for level 20 campaigns, but do not. A true campaign designed for level 20 is going to telegraph that from the start - another level 20 adventuring party that is mostly retired; places in the world even level 20 characters say they are afraid to go to; history involving level 20 characters stopping appropriate threats.  You skip over the anime “and suddenly there’s a new threat!” problem by making that level of play feel organic from the very start. Then the players feel like exceptional heroes - but they don’t feel like they are exceeding the norms of the world, merely standing atop what is established.

Our current campaign has reached the 18/19 level area.  The DM and I have been discussing ways to keep the game going.  One thing is he is up-scaling monsters to provide reasonable challenges.  He is also planning lots of non-combat challenges.

I've played 3 campaigns at level 20, 2 of which were beyond that, where we had additional Epic Boons. They were amazing and some of the best times I've had playing D&D. 

I have not heard of anyone going past 20th level, but I also haven't heard of that many reaching 20th and just as many reaching 15th level, unless it was a one shot.

Going above 20th level would obviously benefit the pure Barbarians and  Monks the most, who would reach the 30 first in their ability scores before any other class. 

Where does it end? Is 30 the absolute end, or do you just keep gaining levels, even though your ability scores max at 30, which is a hard rule.  I mean 30k XP from killing monster is nothing anymore, with exception of those with strange powers who can still put a hurting on at least one PC.  You are still not gods although you might be getting more attention directly from them.

Any who. Most DM's would already be throwing homebrewed monsters, that are unkillable at the PC's anyway.  A better alternative is for DM's of high level PC's is to search the web for high level adventures, even those from the 70s and 80s.  You will find that they are no walk in the park. You would only need to substitute the old opponent stats for the new ones. And they also had 20th and 30the level fighters and magic users in those adventures. 

Not my table, and not a table i play at, but a buddy of mine in europe does a level 27 campaign where, "Nuke it" is often the fail state. It is more political intrigue with these very powerful adventurers now being minor lords, and having to navigate the treachery of royal court. The biggest threat to the paladin is that he will be manipulated into a political weapon and his god ( a homebrewed god of justice ) would be furious with him if he was stupid enough to be taken in by honeyed words and half truths.
It also has the side effect that they can play alongside lower level player characters and those lower characters aren't left in the dust if they are good at the intrigue. 
Though i should note. most of his group are Vampire the Masquerade players so they are no stranger to intrigue play.

But that isn't for everyone, and there isn't much official guidance, so that was HIS best solution. The other option was storming Hell itself, something i was helping their DM design before he said no, and did this Game of The Houses style nonsense. I would love at least some sage advice or a supplement on Epic level play. I ain't holding my breath.

Oh, and i Myself have run epic level games, but imma say it, i was bad at it.