Can the 2021 Apple Mac mini M1 run an 8K UHD display over Thunderbolt?
As soon as MaX get his hands on an 8K display, he will connect his Mac mini M1.
USB 4 will include VESA DisplayPort 2.0 capable of driving 8K and 16K displays; however, this capability has not been fully ratified by VESA or USB and has not made it into the Mac in a prototype state.
It is possible the Mac mini M1's Thunderbolt/USB 4 controller could be firmware-updatable to support DisplayPort 2.0; however, the M1 GPU would require a firmware update to support DisplayPort 2.0 streaming to the Thunderbolt/USB 4 controller.
All of the above is possible.