I have searched a bit and and it seems it can be a lucky end…
Your card:
Is a GCN 1 card and therefore you should be able to run it with the amdgpu driver instead of radeon.
Try this solution:
That force to load amdgpu first and set the necessary options for older gpus which have support for radeon and amdgpu. But it is still called experimental, although its pretty stable and faster on most machines with older still compatible gpus.