Yes and no.
The obvious answer is to make your own device with your own OS and make it better than iOS or android. That used to be difficult, but the quality of iOS and android has been declining for a long time. We're at the point where an alternative could be viable for somebody with deep enough pockets and the know-how.
The not-so obvious answer is we have lots of evidence over the years of the tech sector engaging in anticompetitive and illegal actions with very little consequence. Apple, Google and Facebook colluding not to poach each other's employees. Intel threatening to cut off relations with any computer manufacturer that deals with AMD.
It's very likely that Google and Apple would use their influence and power to kill any viable competitor. So, how do you deal with that?