A Universal linux app store. Contribute to AppOutlet/AppOutlet development by creating an account on GitHub.
I noticed the AppOutlet repo has been archived, but I really liked the idea of one store to rule them all (I.e. snaps, appimages, flatpaks, etc. in one place).
You won't find any alternatives because Flatpak has won the war. Pretty much everyone (except Canonical) hates Snap and avoids it like the plague, and AppImages have significantly dropped in popularity amongst users due to the rise of Flatpak, and the various advantage it has over AppImages. So you're left with only Flatpak/Flathub basically.