Nafeon

I use smartgit it serves me well: https://www.syntevo.com/smartgit/

And it has all 3 of your criteria as far as I can see.

“It magically appears in flatpak only after you’ve installed it by other means”

I kid you not this happened to me 3 times already.

The megalodon author themselve recommended to use moshidon and is considering becoming a contributor there.

This is a valid mention and I agree, but I also have to say that there are companies like the nextcloud corp itself who do offer that level of expertise and are German based and would use the money to improve nextcloud, which is open source, whereas we don’t know how much of the money that Microsoft takes goes into the open source project.

It is like… Each time we showed how well you can live with open source, Microsoft comes around with an even bigger coffin of lobby money.

“…Valve added a special Tux item into Team Fortress 2 only on Linux…”

That’s all you need? Linux exclusive items in your games?