Kernel panics back with most recent macOS update

The panic log is showing the GPU is trying to set a power state and is unable to do so. Either it is trying to go into a low power mode, or exit from a low power mode (I'm assuming the latter). Hardware issues can be intermittent as well and can be the hardest things to figure out. It does not help that Apple techs don't even try to analyze a Kernel Panic report, as they only rely on their service diagnostics and whether a clean install works or fails.

I guess you could try to "Restore" the firmware (or "Revive" it), but I doubt this will have any effect either, but it is probably the only other option before having the iMac repaired except to make sure all external devices are disconnected in case one of them is causing a problem.

Revive or restore an Intel-based Mac using Apple Configurator - Apple Support

Maybe a silly quest ?

After the Wipe and Reinstallation was Setup Assist or Migration used ?

If so, it may have brought back the Exiting Issue back into the otherwise Pristine and Virginal Installation

AMDFramebufferVega10::setPowerState(0xffffff9031bf4800 : 0xffffff7fa088a8ee, 0 -> 1) timed out after 45489 ms

Looks like a GPU issue if you tested a clean install before installing third party apps or restoring from a backup. For this model iMac means a Logic Board issue since the GPU is integrated onto the Logic Board IIRC.

I support thousands of Macs for our organization. I have been finding that the 2018+ Macs seem to have a much higher rate of Logic Board failures and it is starting to concern me. We've had to replace at least three iMac 2019 Logic Board several months ago...the failures occurred close together.

I think it has a lot to do with the T2 security chip since they make things so much more difficult (even the 2016 & 2017 Macs with T1 chips have more issues than older models). Part of it is due to the Logic Board now containing so much more integrated onto them like SSD, memory, GPU, WiFi, etc. Unfortunately when many of these 2018+ Macs fail there is no way to even know which component on the Logic Board is bad because anything you want to do requires authenticating with the T2 security chip. The T2 security chip causes me no end of headaches while supporting our organization's Macs. These 2018+ Macs are just glorified iPads without a touchscreen.

There is nothing you could have done to prevent the issue. Just use the iMac as you wish.

I'm glad Apple is going to replace the MLB for free for you.

Thanks for the follow up to confirm as it helps us and it will help others who find your thread.

Did you have any external devices connected at the time? An external display may trigger something like this, or a dock which provides access to a display even if a display is not connected at the time.

Thanks for the follow up, please keep us updated. And good luck!

Do you have any hardware attached? If so, try letting it sleep with it disconnected and see what happens.