For anime there’s not really activity for episode or Manga chapter discussions, and found that the My Anime List forums ended up filling that void. https://myanimelist.net/forum/
For buildapc checked out pcpartpicker and found they had a forum with people to help and being pcpartpicker the layout of parts is really nice when people suggest them to you https://pcpartpicker.com/forums/forum/27-create-a-part-list-for-me/
For more casual stuff like pics and memes found squabbles has pretty good activity https://squabbles.io/
For NBA stuff found realgm forums with lot more activity for individual team boards https://forums.realgm.com/boards/
For video game deals found this forum https://www.cheapassgamer.com/forum/10-video-game-deals/
It was nice that forums are still alive once I finally tried to seek out communities outside of reddit after all these years
Checked it out and it sure is. When I start my Fite Emblem play through I’ll know where to go now. It’s been common to say reddit killed message boards, but turns out it was really more an insulated view from redditors who got used to just depending on reddit. And there’s something about forums where even few posts that are old don’t make the place seem as dead, since responding just bumps it back up so the thread just gets reused instead of new thread dependence.