I found an app for OpenXR users to display FPS in Vr headsets. Shift+Z is a freeware app on flightsim.to that shows various stats in the VR headset relates to the aircraft but it also show FPS (and you can move it around on the VR display and also only show FPS if you want to hide other default stats). It’s nowhere near as versatile as the FPSvr app for Steam VR but it will help show FPS live so if you want to tweak graphics settings you can see the impact a bit easier than using Developer Mode in MSFS where that large screen is only visible in one eye and you have to take the headset off.