This has a good overview of the more occasional maintenance tasks beyond the one-click upgrades in the dashboard:
Basically some minor server updates every couple months, and perhaps more major server updates once or twice a year.
In my experience so far, this is probably overstating it:
Unless you have a ton of plugins / customization, it’s more like an hour every couple months for server stuff, after you’ve got an initial setup with everything working as expected. (We haven’t yet run into major issues beyond that…knock on wood!)
Only other thing I recall is running out of disk space at one point and having to run this (maybe should be added to the guide linked above!):
https://meta.discourse.org/t/low-on-disk-space-cleaning-up-old-docker-containers/15792/2?u=bts