firmware fails to load on AMD RX Vega 56 GPU

Hi there questions@,

first time poster here, folks from IRC directed me to this list.

I have trouble loading the firmware for my AMD Radeon RX Vega 56. In
autumn i tried Freebsd for the first time (14.3 -release) and couldnt
manage to get the card working, despite all efforts. starting xorg
obviously didnt work, so the system was completely stuck in console.
the same usb-stick which i used for that installation produced working
systems on other machines with no graphical issues of any kind,
although  having verified the integrity of the .img with both the shasum
and signing key, this was no suprise.

the card works fine with various other operating systems, (including
linux, from which the freebsd drm driver is originating from) as well as
under heavy load.

15.0 -release was on its way so i figured i'd wait a bit and see if
the problem would be fixed, but having tried again recently with all
errata patches applied, i still get the same error.

Attached is the output of: dmesg | grep -e "amdgpu" -e "drm" -e "vega"
on a fresh and recent install of 15.0 -release. please let me know if
any additional tests/information is necessary

Im out of ideas myself, but hopefully this is the right place to ask for
help.

Thanks in advance,

-urai