@Mathias this could be related to one of the active issues linked here : Active upstream AMDGPU issues affecting Ryzen 7840U (iGPU 780M) - #8 by paulos VP9 has been having issues :
- Unusual Power draw
- Flickering/freeze issues on Firefox under Linux, I believe but AMD provided a testing firmware that has fixed the issue but they need more time to finish internal testing, see : vaapi vp9 decoding glitches on rembrandt [Reproducer in comments] (#8044) · Issues · Mesa / mesa · GitLab
But none were reported under Windows, they were seen under Linux.