That's really disappointing. I'm not Linux user, but I use FF on Windows work PC. As this is my working PC I don't want to install desktop EN on it (we still have no possibility for selectable sync) that means that I could not use EN at work.
Still using while hoping, that they will come out with some client improvements we are waiting for. And maybe with another plan/tier for users only wanted to sync 3 or more devices.