After some testing with the direwolf20 1.20 modpack,
For some strange reason MFFS causes the gui (any gui) to render out of frame to the bottom left in an HMD.

(EDIT: Forgot to mention, but the gui is still intractable at its normal position. You just cant see it.)

Unfortunately this is all the information i have.

MFFS Vers - 5.1.9
Vivecraft - 1.1.5
Forge - 47.2.0
Minecraft - 1.20.1

Yup, changing changing that setting to false does fix the GUI in VR!
(unsure if i should close issue as the setting now needs to get changed by vivecraft or mffs. unsure if vivecraft can?)

hm they probably have some post shader or something that messes with the render targets

https://github.com/BuiltBrokenModding/MFFS_Classic/blob/d963396d7d344e61b73df7974926c00bd91c8490/src/main/java/dev/su5ed/mffs/render/RenderPostProcessor.java#L43 and https://github.com/BuiltBrokenModding/MFFS_Classic/blob/d963396d7d344e61b73df7974926c00bd91c8490/src/main/java/dev/su5ed/mffs/render/OffscreenRenderTarget.java#L7 could be the reason

@Link-Jon can you check if disabling enableProjectorModeGlitch in the mods settings fixes it?

patially fixed with 1.1.12, gui shouldn't be squeezed into the lower corner anymore, but the forcefield previews don't render with the glitch effect enabled