1. Traditional Distorbution packages. If someone want to go that way OpenSuse Build Service. https://build.opensuse.org/
"The openSUSE Build Service is the public instance of the Open Build Service (OBS) used for development of the openSUSE distribution and to offer packages from same source for Fedora, Debian, Ubuntu, SUSE Linux Enterprise and other distributions.." (Possibly MacOS and Windows)
2. Package Formats (I hope it is the future) we have appimage, flatpak (Redhat backed), snap (Ubuntu backed). Containerized solution with the hope of easier portability and better security by sandboxing type solutions.
Personally I think flatpak is the best of breed with appimage a close second. Flatpak and appimage are the most open friendly. Flatpak using individual repositories which I prefer. Snap uses a central location which i also don't like as much.
Seriously, .deb or .rpm is okay, but what users will really want is a proper apt/rpm repository, which is for sure more effort.
I honestly prefer zip or AppImage. Distribution independent, and it's super easy to get auto updating in Electron.
Shorter term, an Ubuntu PPA wouldn't hurt. Other people have other opinions and litmus tests, of course.