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.
With an increase in mobile Linux (e.g. Mobian and others), they can and will get better. Customers and developers choice and freedom are being nullified, because there are few other options. That has to change.
People sometimes say, "maybe desktop Linux lacks in security, but its privacy is first-rate," which IMHO is silly because if your OS can be completely and totally pwned by your visiting a web page, your opening image file or your using some IDE to inspect some source-code repo, how much privacy do you really have?
GrapheneOS is just as free from data collection by megacorporations as desktop Linux is and has about 1000 times better security.
In a possible future where google decides to continue any new update of Android as closed source, will the community have enough people stepping in to support the development of AOSP? Will google allow the Play Store to run on AOSP? If not, do we have enough apps distributed outside of the Play Store to compensate?
My point is that for an OS that shares more code with desktop Linux (same apps, same DE, same terminal programs, ...) we can rely on the existing Linux community to maintain and advance the OS, and then adapt it for mobile, which I think takes considerably less resources