Not entirely sure of this. There are a number of attempts to make a Linux OS that can just replace Android on phones. I haven't gone there because the tech knowledge required is considerable and they sound temperamental, and they don't work on most devices either. One recent notice doing the rounds was that De-googled Androids were trying to update themselves to Android 12, which makes me wonder how de-googled they really are.

Some phones are designed for other OSs, but I have no special knowledge on that.

Things you can search:

Purism

Librem

Pinephone

Ubuntu touch

The other guy might be right about Graphene, check it out by all means. Really none of this is my field - I just like typing ;-)

Remember that a regular Android settings can make a huge difference to privacy, and there are a number of apps to help, like microphone blockers, location fakers and so on.

Most important of course when it comes to privacy is it is ALWAYS the user not the device that counts the most.

This guy knows his stuff about device security, may be worth a follow: