Projects like OpenXR toolkit support gathering fps statistics, but mainly for real-time overlays not for more rigorous analysis that CapFrameX supports.
openxr code pointer
OpenXR toolkit author doesn't have time to support or enhance.
Perhaps CapFrameX developers could take inspiration or adapt from OpenXR toolkit's code?
[ SteamVr would be useful to a lot of folks as well, but that would be different code ]