Right now I have it running with a dual 6pin to single 8pin adapter.  Running ok so far with stock speeds, fans, etc.  Doing some test now.
Welp, here's where  "upgradeable" takes a turn. The EVGA FTW3 Ultra 3080ti, it fits. However, there aren't enough 4pin connectors from the PSU to power the thing. Three 8 pin, or 2x8pin and a 6+2pin are needed. The PSU came with 2x8pin and 2x6pin. Friend of mine is a little upset. 
Upgrading from Dell 3080 to EVGA 3080 Ti, impossible?