I got a Xiaomi POCO F5 recently that might fit all your Must criteria (idk about size), but another Xiaomi may work. Just if you're located somewhere that doesn't use the Type C Socket, you may need an adapter or a different 67W charger
Xiaomi has a bootloader unlock process, though it is a bit involved. You've gotta put your SIM in the new phone, create a Xiaomi then you've gotta run their bootloader unlock software, which needs a Windows Computer, idk if it runs in a VM, if thats an issue for you. Then you've gotta keep your SIM in the phone and have it on for a full 7 days and then run the bootloader unlock software again, which will wipe your phone, but now the bootloader is unlocked
You do have to use MIUI for a week before you can wipe it and try something else, but once you go through it its fine. I've been using Paranoid Android on mine with no issues.
This should apply to any recent Xiaomi phone. Just something for your consideration