"As a user, I want to download an application from the original author, and run it on my Linux desktop system just like I would do with a Windows or Mac application."
"As an application author, I want to provide packages for Linux desktop systems, without the need to get it 'into' a distribution and without having to build for gazillions of different distributions."

Another distribution-independent packaging format. See https://phoenixnap.com/kb/flatpak-vs-snap-vs-appimage and https://thp.io/2019/flatpak-vs-snapcraft.html for comparisons with snap and flatpack.