That would be nice, plug in usb-c to a display and keyboard.
But there's another way, can't someone implement their own implementation of the core google services apis and then you can just load a regular app off the app store and run it? Google would absolutely want to block this as their control and monopoly depends on it. But it shouldn't be against the law.
It's obvious, so it means someone must have tried and it was not reasonably possible.
It's obvious, someone has tried it, it works and is commonly used on those more FLOSS-conscious and de-googled "ROMs" - it's called microG. It's not Play Services that are the limit, it's device attestation.
Same with the device proposed by the parent - I can plug my Librem 5 in to a display and keyboard and it runs a regular GNU/Linux distro while working well as a phone, without Halium or any other Android bits.
We had these things for many years now, just look around harder :)