And ESR, but that may not be normally distributed in Linux distros. It's not in Arch Linux.
There's no hassle free solution. Only way to run your own code on normal branded Firefox release is to rely on third party signed extensions (eg. Violentmonkey), but that's not really hassle free either if you have 10s of userscripts and multiple browser profiles, and you have to trust some third-party to not go rogue. I got pretty terrible malware from mozilla add-on store in the past.
There's no hassle free solution. Only way to run your own code on normal branded Firefox release is to rely on third party signed extensions (eg. Violentmonkey), but that's not really hassle free either if you have 10s of userscripts and multiple browser profiles, and you have to trust some third-party to not go rogue. I got pretty terrible malware from mozilla add-on store in the past.