Hi Guys,
I got the exactly same problem last night, I upgraded to 6.8.1 a few days ago and rebooted last night and got the same error immediately. Tried all safe boot options but no luck. I thought maybe my flash drive went bad, so I created a new 6.8.1 on another usb stick, it booted with no error. So I ordered another new Sandisk usb stick which will be delivered tomorrow morning.
On the server I have:
AMD threadripper 1920x
ASRock X399 Taichi MB
16GB Samsung ECC Memory * 4
HGST 8T disk * 11
Micron U.2 1.92T SSD cache drive * 1
SATA extension card * 1
Tomorrow I will remove all my data disks, backup my old usb stick first and check if there is any problem with it. If the problem is not with it. Then try to downgrade to 6.8.0 to see if this is related to 6.8.1.
I would like to know, if at the end I have to recreate new USB stick, can I copy all files on current one to the new one, then manually replace all system files with 6.8.1 install package, make it bootable and boot into GUI and go through the Registration process? Does it work really?