For several years I was using TTRSS, but this year I moved to a Miniflux instance that I host at home. I couple it with an instance of Wallabag for saving articles for later reading. I like the experience of the Miniflux PWA app better than TTRSS.

Speaking from experience from the last five years, it’s been pretty good for me.

Nextcloud has chat capabilities. Perhaps it might be overkill for chat alone but presumably you also want some collaboration with documents.

By any chance is this from Andrew Tanenbaum?

Minecraft has been suggested here but there’s also Minete St, free/open source version. The experience isn’t exactly the same but the basics are there. Works with PC and Android. You can also run one of the computers as a host and you can do multiplayer. Absolutely no microtransactions.

Budibase.