Thanks for your reply.
I tried to force steamvr_win64.json, and the performance are really bad, but it works !
So I guess it confirms that the problem comes from OpenXR:
1 - I can’t run the OpenXR Developper Tools
2 - MSFS works in VR through SteamVR
Problem is : I don’t know how to force a OpenXR repair. I really don’t want to reinstall W10 just for a small module fault…
Thank you for your help !