Firefox Nightly Debian and Ubuntu Packages

I'm one of them. I prefer to avoid flatpak when at all possible.

Yup I always prefer proper packages instead of flatpaks or even worse the snaps. In fact I wish more software developers woulduse Open Build Service and create many packages for many distros: https://openbuildservice.org/

Agreed. I prefer proper packaging and a clean system. I remove any flatpak services that get installed. So far there is a total of two AppImages that I've ever needed to use and those ran inside a firejail sandbox.