https://tuxphones.com/capyloon-firefox-os-b2gos-linux/The forks sound loaded with adware so I'm skeptical.
But, I think this sort of thing shows that Google and Apple's, iron fisted grip on the mobile OS market is weakening and that Google at least would have a hard time using a heavy hand to try and take back control because they are under so much scrutiny by regulators.
Therefore, I expect more OS "revivals" now while mobile OEM handset manufacturers and ISP's are less afraid of Google. Most OS's won't take but privacy and security are both in the public mind.
