Kernels are 5.0 and 5.1-rc1.
Is it just kernels 5.0 and 5.1? There haven't really been any display
related changes to radeon in ages. Possibly a duplicate of:
https://bugzilla.kernel.org/show_bug.cgi?id=198123
No, I just put the card in and tested with only the current kernels I had.
I can get some older kernel and test with that if that is of any help.