This is a quick overview of where to find some good resources when getting started with Godot and XR
First is our documentation: XR — Godot Engine (stable) documentation in English
Support for any OpenXR device comes out of the box, but if you are using an Android based device (Quest, Pico, HTC Focus 3, HTC Elite, Magic Leap 2, Lynx R1, etc.), there are extra steps to follow that are detailed in the documentation linked above.
Godot does not implement advanced features in the core and relies on plugins for this. A popular plugin usable when developing with GDScript is Godot XR Tools:
But there are other plugins including C# based implementations, check out the asset library and try some out!
Finally some popular Youtube channels with tutorials: