The point isn't "run the Linux kernel on a phone", the point is "run an non-big-tech OS that respects the user's privacy and choices". See also Google's recent announcement regarding locking down Android app installation to "protect users"
That's not what was said here, though - and also not something that's going to become a viable major platform.
The folks who care about privacy can't agree on the definition of a privacy respecting phone, so whatever you make some of them will be unhappy. 99.9% users care way more about price, availability of apps, and hardware, in that order. App developers will only write apps for the platform once it has sufficient users, and users will only switch if the platform has sufficient apps.
I guess I’m not clear what the point would be. I suppose you could build a phone that uses more of the gnu ecosystem than Android does, but you’re not going to run desktop apps on your phone because none of them are made for the phone. It would be a bad experience. So it becomes (Desktop) Linux for (Desktop) Linux’s sake.
Isn't there already a viable, widely used Linux based phone OS called Android?