Not directly answering your question, but if you haven’t already you should take a look at the end of life disaster recovery repo.
Cataclysm: Dark Days Ahead. Zombie survival roguelike, forked from the original cataclysm by whales. Also check out Cataclysm: Bright Nights which is a fork of CDDA that makes it more gamey like the original, and less like you’re playing 2d arma.
Sunshine and moonlight are open source implementations of nvidia’s game streaming protocol they created for the nvidia shield. You can use it to remotely use your computer from your phone, not just for games. But of course the primary application is game streaming. As long as the game can run on the host (sunshine) computer, you can remotely play it on the client (moonlight) device. I’ve used it to just launch steam in big picture mode and then select what I want from steam.
You have to add them manually, either by url or with the built in search. For example, you can add newpipe by searching sources and checking github as a source to search. It will then show you repos that match newpipe, which usually is the regular newpipe repo and then a bunch of forks of it.
Obtainium isn’t for finding FOSS apps, it’s for installing them. To find them, you can check out existing repos such as f-droid or izzy, or you can ask around. This post has a bunch of recommendations in the replies
Obtainium lets you install FOSS programs directly from the developers source. You can get updates from the github/gitlab of app developers before they get uploaded to F-droid.
I’m guessing they meant This Old Tony