I finally got my EliteDesk 800 G2 TWR running with Dual Monitors (see below)
I tried to follow
@sakoula GitHub but kept ending up with boot loops before even booting into the installer.
I did a vanilla install - Created USB with UniBeast, installed clover using Clover Configurator and then used
@PaintArm2 EFI folder.
All worked with Graphics Acceleration but no dual monitors.
I chatted with sakoula who took time of his own to try help me figure out the dual monitor thing, but we came up with nothing. We reverted to his EFI and Kext's and made a bit of progress but it still did not work. We think its because Im using DP-HDMI or DP-DVI cable (no adapters) and not DP-DP.
However, happened to have a Lenovo USB3.0 laptop dock that has DisplayLink standard. I installed the generic DisplayLink macOS drivers, rebooted and now have Dual Monitors working! W00000T
Only think that is missing is higher USB limit but TBH I may not need them anyway, especially now that the dock also has USB
So once again, a huge thank you to
@sakoula for (first of all) putting together your GitHub guide and also trying to help me out with my build - what a champ.