My home generator is automatic but you still need an ups because the transfer switch and power on process for the generator isn’t instant. Takes like 10-30 seconds depending on how cold it is and how recently I serviced the generator.

You also ideally need a higher quality ups that can handle the shitty power coming from a generator, although the overall ups doesn’t need to be as “hefty” as a result. My ups is the kind that has extra filtering and stabilization of incoming power. My old ups was a cheaper cyberpower and it died after a few months of generator usage (we lose power here roughly every 4-6 weeks, thus the auto generator). The cheaper cyberpower would be fine in the majority of home circumstances tbh otherwise.