[dTal]

This is really overcomplicating it. Most mainstream end user Linux programs - including Firefox [0] - are distributed through archives you just unpack and run the binary inside, same as most Windows freeware. AppImages are just self-extracting versions of this. Most of the other formats you mention are for distro package managers - these aren't distribution formats and it's not the responsibility of the program authors to package for every distro, nor is it required for a package to be in repositories for people to run it.

Just ship an ELF binary in an archive. Include any files and libraries you need. Compile against the oldest glibc found in any system you care about supporting. That's all you need.

[0] https://download-installer.cdn.mozilla.net/pub/firefox/relea...