Hello,
Is your Monitor connected to the dGPU (dedicated GPU and not the discrete one) … In some cases you either disable the iGPU from BIOS, or go with something like:
DRI_PRIME=1 <command>
to use the dGPU …
Also, make sure you actually use the AMDGPU drivers and not the Radeon drivers.
Follow this [HowTo] Provide System Information and share that information here, so we have more context.