After some more hours fiddling around, I was able to get the drive to boot with my old Mojave install stick. I am not sure what exactly happened but I guess my EFI partition or files there-in got corrupted somehow. I ran diskutil repairVolume on both the Macintosh HD part and the EFI part and neither came up with errors.
I ended up re-running Multibeast, following the instructions from the
GA-Z390 Designare post and put my original custom SSDT and now it boots again from the HD. Yay!
The recovery was touch-and-go for a bit, because of the certificate expiration on the old Multibeast 11.3 for Mojave. Setting the clock back to 2019 worked, but the install took 40+ minutes to complete, I can only imagine it was hitting some 2-3 minute web timeout for every install step due to the non-functional internet because of the time-clock difference.
What I am not understanding is why the subsequent post-install Clover Configurator setup steps didn't complete according to the guide (I switched the time back to present before running configurator). Particularly the SMBIOS and System Parameters settings are not filled in automatically like they seemed they should according to the guide. Attached is a pic of my current / new config vs my 2019 once-stable config. Should I copy some of these values over or leave be? I am able to log in to Messages and Facetime and my iCloud account seems to be working.. although it has asked me to log in again once now because of some vague services error. I can't understand why the Bios ID Version would be different either.
Should I update these values?
View attachment 555367