From my observations I see two groups of apps/websites, one being feed based communities/social media and the other being more communication based platforms that don't have feeds and rather are more conversation based. Here are a few I've used or taken note of.
Twitter - used to be one of my favorite social media apps, went downhill as I barely see the posts of people I follow :(
Bluesky - started off great & has close-knit feeling, then the team mishandled racism against Black individuals :( I personally have hope it could be revived as I love only seeing the posts of people I follow, still keeping my account for the time being.
Geneva - a new app I came across, I don't know too much about it. It aims to combine the qualities of Facebook groups/GroupMe with Slack/Discord. I'm gonna keep my eye on this one for sure! More info here: Geneva Intro.
Mastodon - I personally haven't used this one, I see it touted as a Twitter alternative. From the looks of it, seems pretty Reddit based.
Discord - I absolutely love the Baddies in Tech Discord server. It's the best managed server I've ever seen! There's a few other Discord servers that I'm a part of but they tend to be overwhelming for me, so I have them muted & check on them once in a while.
Slack - My favorite workspace is Virtual Coffee. Overall a great and supportive community. I'm in a couple other tech Slack workspaces too.
Forem - Getting a little bit meta here as DEV itself is a Forem! I'd love to have a community on the internet with everyone in tech that I follow on Twitter in a feed based community as well as have the ability to communicate with one another via replies on various topics. Some people I follow on Twitter have such a large following that I'm not able to converse/interface with them as much as I'd like. I personally haven't experienced creating my own Forem though I definitely can see it's a great option!
I'm interested in hearing others' opinions. Which platform is your favorite? What do you think the future of communities and social networks on the internet will look like? I appreciate your thoughts on this topic!