As for FirefoxOS I never understood the point of it.
OpenMoko tried to be an open smartphone platform and failed.
Nokia did it for Symbian OS with web widgets and it failed.
Palm did it with WebOS, with the plus side of allowing C++ bindings for games, and it failed.
Android and iOS allow for web widgets and cordova like apps and there usually have bad feedback from users vs native apps.
Windows Phone allows for first class development with web based tech and few bother to use it, rather CoreCLR and WinRT.
OEM and network providers always have the final word, they learned not to let others follow Apple's footsteps.
That was a very far hard attempt from the begging.
I rather see Mozilla spending their efforts in Firefox, Thunderbird and Rust.