I found that on old forums I did get to know the people regularly posting on them quite well over time (and they got to know me). On reddit and lemmy not so much, or do you have any idea about anything I’ve posted before (because I don’t know anything about you).
I follow several news organizations, bloggers, activists there. For example you can get Linux news from https://techhub.social/@LinuxToday or posts from Richard Stallman’s blog at https://mastodon.xyz/@rms or the EFF is https://mastodon.social/@eff – of course those aren’t the only accounts I follow, just a sample of ones you might be interested in that have recently posted things.
You can also follow hashtags on Mastodon, that sometimes helps me find accounts to follow. Recently I have however been unfollowing more accounts than I’ve been newly following because my feed was getting spammed with too many things that I didn’t find very relevant.
ETA: you can also follow https://social.growyourown.services/@FediFollows if you are very desperate for random suggestions for things you could follow