If it's free and open source and it's also software, it can be discussed here. Subcommunity of Technology.
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I'll second IRC. I don't need my chat to be e2ee, and encryption has made Matrix a much bigger pain in the ass than it's worth to me.
Forums, too, though I'm a big fan of the distributed social media space. Lemmy has an experimental front-end based on phpBB, and I would love to see someone take that idea and go whole hog on it to create proper federated forums.
Instant Messenger was the shit back in the day.
uMatrix browser extension. It has been marked archived by Gorhill, last release is two years old, you are supposed to just use uBlock [Origin]. However, it still (luckily) works fine and is exactly what I want. (Sure, I won't install this for my parents.) The GUI to simply choose what you want the site to be allowed to do is perfect.