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 tried it on my Nexus 5 as well. It didn’t work well for my needs at that time, so I went back to putting Android on it.