Indeed for simple elements Label3D and such childed to the XRCamera3D work well as a HUD.
The other option is to use the new composition layer objects in Godot 4.3 to present a 2D UI. They need to be children of the XROrigin3D node so you need to make them follow the players head by updating their position but when natively supported by the XR runtime, there is a noticeable quality improvement.