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.
If its only cuz of the unlocked bootloader have a look at DivestOS, Graphene or Calyx
Edit: i use my ING Banking App on my Pixel 6 with graphene and before on my OP6 with Divest
Yeah my next phone will probably be a pixel specifically so I can load it with GrapheneOS.