The news is out. 
The flip_done timeout error has finally been fixed after nearly three years now.
Turns out the aforementioned bisect by Michele Palazzi was just the beginning of hunting down the bug. Patches after patches, then patches for the patches, then regressions but finally after three more months it’s done. phew
Fingers crossed this is really it. 
Should you experience a flip_done timeout despite the updated kernels of the new [Stable Update] 2026-08-12, please note the previous posting with AMD’s instructions. 