Phone based AR is a mess because while openxr did make some specs around it, google and apple never adopted them, so you need to use their proprietary bullshit instead. I don't have any experience with it myself.
https://forum.godotengine.org/t/does-godot-4-support-ar-for-android-and-ios/88658/3
MOTION TO MAKE A RULE THAT USING ALL CAPS IS AGAINST THE RULES