Small local ultras should go ahead, that is how my 320km worked out in September. City races are not happening before a vaccine is wide spread.
Don't worry snout your ultra. The whole point is the distance is so huge that it is hard to comprehend how it would be possible. Pacing is very important snd kind of the opposite of a marathon. Your race pace in an ultra will be slower than your training pace, especially on the hills. And then it is just pure mental. You will feel totally exhausted beyond anything you have ever felt before and your mind screams at you to stop, get a quick shower and start on the beers..., but the crazy thing is your body is still working. You can still move, even if not a fast run. I have almost never got to a poibt where the muscles just were not working enough to do a reasonable jog on flat ground or hike uphill faster thsn the tourists.
Then the really crazy thing is, the same applies to sleep. You can be literally falling asleep on your feet, hallucinating like crazy after 2 hours sleep in 60 hours of running, yet your legs still keep going.
Physically, you just never stop if enough food snd water goes in. But you need that mental fortitude.