This may be true for games, but it's less of a problem in general. If you don't want to release the sources and have it handled downstream, you can always statically-compile everything and call it a day. Most commercial vendors tend to do that. Display managers are pretty much irrelevant, I can't think of any application that cares if you're running gdm, sddm or anything else; the ALSA backend pretty much guarantees everything is fine in the sound department.

I guess it depends on how many dependencies you're relying on and on what those dependencies are, but the process is pretty smooth.

If they manage to develop things for Android, it can be done for Linux, too.

(Source: developed and packaged a commercially-distributed Linux application. Not too painful a process.)