There are no steam gauge backup instruments in the F-35 and there is no HUD either, everything relies on the HMDS and the MFD. If the MFD happened to not work, that would be fatal because (almost) everything depends on it because it's like a almost like a Tesla console. GFL piloting an F-35 without an MFD in IMC.
https://www.codeonemagazine.com/images/media/Front_Office_01...