I also daily use Firefox, Thunderbird, VSCodium, Signal, KeepassXC, DAVx5 and Radicale for calendar syncronization.
What I don’t use each and every day but what are among my favorite FOSS projects are KiCad for electronics design and CoMaps for navigation.
discuss.tchncs.de is tech-focused :) It seems like there are no communities for games and comics yet though.