According to the always great Atomic Rockets site, their thesis is that it’s a fucntion of RPM - 2 RPM is fine for most people, and anything above that will require training. For a shirtsleeves 1g environment, at 2 RPM you will need it to be well over 100m in radius.

I did a campaign using FFS as the ship design system years and years ago with a large TL 8/9 empire. All of their ships had spin gravity (normally only deployed while they were in jump). However that made the smallest possible ship in the 5 - 10k Dton range.