As noted
here, I need to switch my patched connector types to HDMI <00080000> for Monterey. I have found that my DP->DVI video adapters work with Big Sur 11.6.2 when using patched connector type HDMI (instead of DVI), so I will be modifying my EFI baseline to use type HDMI. My next posted EFI will include patched connector type HDMI instead of DVI.
EDIT: Note that in order to use DP->DVI video adapters with this rig (CFL UHD630 iGPU), I must use a "mobile" framebuffer (I'm using AAPL,ig-platform-id 0x3E920000). A "desktop" framebuffer (e.g., AAPL,ig-platform-id 0x3E9B0007) with DP->DVI video adapters results in booting to black screens. This has been true for as long as I have been patching the HP EliteDesk 800 G4/G5 Minis.
EDIT2: I was reviewing older posts and see that
@fennec62 may have been the first to mention something related to this
here. Unfortunately, I wasn't trying to solve my own Monterey blackscreen problem at the time and didn't pay enough attention. Well done,
@fennec62 for being the first to find this solution in this thread.