The thing that stands out to me the most in threads like this is always the things DMs ban, specifically for balance concerns, that just....aren't outside the power band of the PHB.
I get banning the Scribe if another player wants to play a sorcerer, because that's easier than giving the Sorcerer extra special better damage type swapping, and some of y'all care a lot more about niche protection than I do, but because it's too powerful? I am a confuse.
Even the terrible 4Elements monk can play alongside Rapier and Shield Vengeance Dexadins, and Hexadinorers can play alongside Sorcerers from the PHB, and unless your players are really counting total damage per round/combat/day on a regular basis, none of it should be "broken", IMO/IME.
But, I am also of the school of thought that we uplift that which has been left wanting, and only then think about bringing down that which has a little more.
In that light, I have very few houserules.
1. Sorcerers can choose a signature meta-magic at levels 5, 11, and 15. They have Proficiency Bonus number of uses of these meta-magics (collectively, not individually) at no spell point cost, every day. 1a. They also have broader latitude in improvising spell effects than I give to other casters.
1b. Sorcerers get to regain Cha mod sorcery points buy taking a ten minute breather (can be done as part of a shortrest), PB/LR.
2. At level 1, everyone gets either a free feat, Theros/Theros inspired supernatural gift, Strixhaven Background, or similar setting specific character option. No, there are no restrictions on the feats. No, it hasn't caused any balance issues. The few human PCs we see haven't taken GWM+PAM at level 1, but I just don't see it being a problem if one ever does.
3. We do a +1 and a feat at ASI levels, instead of a choice between, but that may change as rolling for stats has been moving back toward being our norm again. That extra +1 was more there to help make up for 5e's very low point buy, than for any balance reason, but we haven't decided yet.
4. Crits are max damage + roll.
5. New and in testing- Monks can regain half their ki points by spending 1 minute in concentration, PB/LR, and Warlocks can do the same to regain 1 spell slot.
That's about it. I have some rulings that differ from Sage Advice, like treating the reaction attack in the Mage Slayer feat as interrupting the spell, and thus requiring a concentration check just like if the caster had readied the spell, but since that is just the reading of the spell I and my other DMs had until SA informed us all of the official reading, I wouldn't count it as a houserule.
The only thing I ban is evil characters.