Once the rewritten "amdgpu" driver came out, things got much better. The first few cards created after that (IIRC the Polaris GPUs, RX 400's), the situation reversed. I still have had occasional issues with various Nvidia cards (normally driver updates breaking things), but for almost a decade now, I have not had issues with AMD GPUs under Linux.
[0] Except for pro features while using workstation cards. You need to use a proprietary driver for those, but even those share a lot of code with the open source driver.