This looks like a similar but different problem. https://www.linuxquestions.org/questions/slackware-14/dual-monitors-blank-screen-on-one-when-using-displayport-error-clock-recovery-failed-4175744481-print/
It seems most likely a GPU driver issue. I run Ubuntu on servers mostly, and have never used a Radeon card.
Good luck!
I may, but I can’t see it! 😉