Today 10 years ago I went to Poland to buy a Phone with pre installed #Firefox OS on. The Phone was a Alcatel One, so very shitty. Two years later I installed Firefox OS on my Nexus 5 instead.
It was a very good concept, but sadly rolled out on too shitty hardware so it never caught on.
I disagree. Most phones can only run proprietary operating systems and the modem runs its own proprietary operating system, which very likely has access to system memory. Your phone carrier tracks you everywhere you go and can listen to your phone calls.