On both social media I still use, I followed bunch of indie ttrpg devs. I had to unfollow the ones on tumblr because they don't talk about anything but how much they hate D&D, up to including writing weird headcanons about people who help popularize it (I actually seen someone on tumblr claim Brenann Lee Mulligan must HATE D&D because only dumb people could like it and is only pretending to like it for clout) or bich about how D&D fans only want to play D&D and get mad when you tell them they're complaining about a small minority.
meanwhile indie ttrpg devs on Bluesky constantly promote their work and inform of sales of their products. I found many cool games through bluesky, meanwhile nove through tumblr.
I imagine that Brennan Lee Mulligan walks a fine line as a public figure.
He still plays D&D often enough to (seemingly) not alienate people at Wizards whose work helped launch his career.
But he also plays significant amounts of other games, including some that I think are Indie developers, like Kids on Bikes.
I'm sure he's aware of the issues and concerns in the community around D&D under Wizards - and probably shares many of those same concerns, as a fellow player and DM.
But, yes, the idea that Brennan secretly hates anything sounds pretty silly. Brennan has been pretty direct with his epic rants about things he really hates.
I'm pretty sure Critical Role has also done some Monsterhearts stuff, which is also indie. I don't personally like that game for a myriad of reasons, but I do believe Mercer ran it one or two times.