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.
It was quite slow because of the hardware, it sometimes wouldn’t recognize touches, and the software had so many bugs like that when you got a call, you couldn’t take it because there would be some overlay over the button to take the call which would steal the touch most of the time, etc.