well, today i (partially) realized why my basic drivers don’t work: the preinstalled packages amdgpu and amdgpu-dkms seem to not work due to amdgpu-dkms being unconfigured. tried configuring it and got the same error. around about there my system stopped using even the iGPU and i had to uninstall some other drivers (thanks @lena@gregtech.eu )
It is true and has been my experience for the last decade or so. Unfortunately, OP is trying to use a GPU from 2015 that’s still based on GCN 1.0 with the newer amdgpu driver stack, which is not officially supported. Effectively, OP is getting a taste of what it was like before AMD started pouring ressources into their open source GPU drivers.