So I have ran into a strange bug/issue regarding my niche setup. (Though I assume there are many other GPU rendering types out there with similar setups.) It seems like Photoshop's GPU acceleration bugs out and does not display/work correctly when you have 2 GPUs in NVLINK, and 1 GPU that is not a part of the NVLINK group driving the monitors. Photoshop will correctly detect the display GPU in the GPU compatibility check but it will not display correctly anything in the canvas. It just "locks up" what was displayed.
If unplug the display GPU from my monitor and instead plugin one of the NVLINK'd GPUs then everything works fine as expected. So it seems related to NVLINK interfering with the display only GPU driving Photoshop correctly. I do not have this issue with other programs, and it is odd that the Photoshop GPU check detects the GPU just fine.
It would be great if I did not have to change the HDMI cord out every time i need to use Photoshop. This is a common GPU setup for people who render on GPU renderers with multiple GPUs, they use the NVLINK'd GPUs only for rendering and a single GPU for monitor display and running any other apps/OS resources. Thanks!
Machine Specs:
2x 3090 NVLINK (Headless / No Monitor Output)
1x 2080ti (Driving Dual Monitors)
OS Windows 10
Photoshop 20.0.2 Release