Some of my favorite communities that are fun and active are:

• !bicycles@lemmy.ca
• !cyberpunk@lemmy.villa-straylight.social
• !foss@beehaw.org
• !games@sh.itjust.works
• !linux_gaming@lemmy.ml
• !steamdeck@sopuli.xyz
• !technology@lemmy.world

r/RedditAlternatives is another one that might be worth mentioning instances on.