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 )
I had to install a pacman package and change a config so my system would use vulkan instead of opengl. Other than that, nothing should be needed.