AMD GPU next to an NVIDIA one: no video output from the former

Hi everyone!
The GPU I’m talking about is an AMD Radeon Pro WX2100. Latest dmesg output, specs, system flake(yes, I stole it from hlissner. Shame on me). So far, I checked out this issue on github, and this thread, to no avail.

I’m trying to run it next to an 1080ti in order to set up a VFIO system, but this AMD graphics card is just too stubborn to just work. Dmesg, system logs, X logs seem to look so disgustingly well I don’t even know where to look - yet the display output is not there. Any ideas?