Older AMD? Any AMD card or igp made in the last 14 years works out of the box with Linux, save their newest GPU arch.
The open source driver still doesn't provide feature parity with the proprietary one that Ubuntu LTS dropped support for.
https://www.omgubuntu.co.uk/2016/03/ubuntu-drops-amd-catalys...
Namely hardware video decoding and OpenGL version.
So this thing about marvelous open source AMD support, depends pretty much how much luck one has.