¹ IRC client for macOS: https://github.com/Codeux-Software/Textual
² Un/archiver for macOS: https://github.com/aonez/Keka
There is https://github.com/neilalexander/seaglass but it is very incomplete
On Android I've been happily using F-droid as my primary marketplace. There's lots of high quality apps that are completely open source. But I think some of the more complicated apps end up having maintenance issues. It can be hard for developers to justify spending lots of time fixing bugs and providing support if they're not getting paid.
One option for solving this is to charge for the precompiled version, while freely providing the source. This way users retain source access and the project gets funded. That's what Textual [0] does, which played a big role in convincing me to buy a license.
The software is on GitHub (https://github.com/Codeux-Software/Textual) and you can compile it yourself and, thus, remove the "you gotta pay" checks and such. If you can do that you are free to do that... or you can just pay for it and don't have to bother. It's not crazy expensive ($5.99), but I decided to go for the former just because it was more fun to me. If I had used his software for much longer and more often, I'd have eventually paid for it, I suppose.