Or they could just redirect to already widely used services like Patreon, ko-fi, Monero, or a PayPal address. Doesn’t have to be more complicated than other apps. :)

I recommend this quick read: https://www.gnu.org/philosophy/free-sw.en.html

Well, libre software does not have to be gratis. The FSF even endorses charging money for free software, or at least asking for donations.

I think pushing them to F-Droid is a good idea regardless.

I’d be interested in developing very presentation-first casual games similar to Candy Crush.

Steam is a monolithic kernel for the GNU/Linux operating system.

Another reason why production should not be based on competition.

I had the opposite experience. Games that worked only after shady DLL replacements and third party mods, and barely at that, worked at one click on GNU/Linux for me.