Next I would suggest downgrading mutter which is used to render gdm3 (and because the 3.26.1 release happened at the time of the bug too) but comment #21 seems to suggest that's already been tried.
Still, we can't definitively exclude Mesa or Mutter fully because there's always a chance that some mistake was made during testing. And there's also a chance that different people are experiencing different bugs. Please keep experimenting...
Thanks. We can /probably/ exclude Mesa then.
Next I would suggest downgrading mutter which is used to render gdm3 (and because the 3.26.1 release happened at the time of the bug too) but comment #21 seems to suggest that's already been tried.
Still, we can't definitively exclude Mesa or Mutter fully because there's always a chance that some mistake was made during testing. And there's also a chance that different people are experiencing different bugs. Please keep experimenting...