I actually have a similar issue again too, but it appears sufficiently different (w.r.t. log messages and system fan activity) that I reported it as a separate upstream bug at https://gitlab.freedesktop.org/drm/amd/-/issues/1329. But the timing w.r.t. dropping the old Picasso firmware admittedly looks a bit suspicious. I am currently trying to narrow down the affected kernel version as per upstream request...