There must be a tool that allows you to build packages for multiple systems in multiple formats (deb, rpm, nix, flatpak, snap, etc.). Does that not exist? After 20 years of these systems existing, somebody must've tried...
Also, it's clear that once again, open source needs some kind of funding model, because it's a little crazy that a project like this can get so popular so fast, the dev flooded with praise, thanks, and issues but not money to maintain and develop it.
Problem is that distro1 has req-lib2.5.3 while distro2 has req-lib2.7.8, but your project was developed on distro3 with req-lib2.9.5 so you have to deal with every distro having different lib versions and compatibility issues that come with it, not just different packaging formats.