CapnZapp
Legend
Sorry but in your understandable drive to make essentially a yes/no question you made the poll too simple.Inspired by some of the threads going around. Pretty simple question. In your gaming group (not a pick up game with people you don't know, and AL is excluded for obvious reasons), do you allow any sort of 3PP material or homebrew material? Or does your group stick with official RAW published by WoTC only?
My answer is: no homebrew or 3PP under the control of the players
That does not mean I as DM can't or won't make stuff up. I may even make new stuff (like magic items) available to the PCs.
But no character build options from any source that isn't official WotC. If it is 3PP or homebrew it is never anything the players can count on without direct and overt DM intervention.
A strategy borne out of necessity in the 3E era. And still way too much DMs Guild material is hopelessly generous. Most official add-on content is outright stingy with powercreep, and unless a 3PP makes itself well known* to adhere to this policy I won't have it.
*) So well known, in fact, that it transcends the guild and starts to permeate these very forums. I'm never at DMsG, so I wouldn't know unless "Book X from Y" stands out from the crowd so much so people start referecing it here. And even then, I need to hear specific evaluations of the "Book X is really up to par".
So far, about the only 3PP caught on my radar has been the C7 middle-earth book. And it promptly fell on its face with a couple of extremely ill advised last second additions (after the initial pdf; just before print with no time to react to the collective "Noooooo....")
TL;DR: I had to answer no. Just don't assume a no means the monsters can't have homebrew abilities or homebrew loot.