My 3 year old (turned 3 at the end of January, for reference) dropped his nap about 3 days into stay-at-home. I suspect part of it is we just can't run him crazy like they do at daycare.
So we do quiet time, and that's a bit of a mess. It's more like one hour of "Mom? MOM? MOM! I need you!" every five minutes. And the first two weeks was extra rough, one of us had to physically stay in his room. No at least we can attempt to work. We got a timer so he can see how much time is left (like these:
https://www.amazon.com/visual-timer-kids/s?k=visual+timer+for+kids) and that has helped a bit.
We pushed bedtime up by 30 minutes because otherwise it's impossible. Late afternoon is a lot of making things as calm as possible and avoiding landmines. Also a big snack with lots of protein around 3.