Update: the latest beta of iOS 14.2 seems to mostly solve the problem for me. The caveat is I can’t get any automations to run between 12AM and 1AM local EDT time.
My theory: This bug was preventing automations after 12AM somehow by getting the system ‘stuck.’ I think they’ve fixed this from breaking the whole system, but it is odd that there’s a one hour gap where time of day automations simply won’t run.