Using desktop linux phones and trying to force that as a norm would set privacy and security back substantially.
The inverse of what you suggest, which is Android with desktop linux app compatibility, would be a huge step forward, and is already much closer than you might think.
Modern phones have substantially better VM support in the hardware than in previous models, and it is maturing at a very fast rate. We would be able to run linux VMs on Android, paired with desktop mode, with evidence for USB passthrough for an externel GPU in AOSP
There is also evidence that we will be able to put desktop linux app icons on the Android homescreen and using them in an app-like fashion.
This would use the more secure host to run the VM for the less secure OS.