The 7850 was from the transition period where the radeon development was ending but it also didn't get immediate amdgpu support. An earlier card will use radeo

The 7850 was from the transition period where the radeon development was ending but it also didn't get immediate amdgpu support. An earlier card will use radeon and be easy to setup, a later one will use amdgpu and be easy to set up. That generation takes a bit of work.