I recognize this will vary depending on how much you self-host, so I’m curious about the range of experiences from the few self-hosted things to the many self-hosted things.
Also how might you compare it to other maintenance of your other online systems (e.g. personal computer/phone/etc.)?
Not much for myself, like many others. But my backups are manual. I have an external drive I backup to and unplug as I intentionally want to keep it completely isolated from the network in case of a breach. Because of that, maybe 10 minutes a week? Running gentoo with tons of scripts and docker containers that I have automatically updating. The only time I need to intervene the updates is when my script sends me a push notification of an eselect news item (like a major upcoming update) or kernel update.
I also use a custom monitoring software I wrote that ties into a MySQL db that’s connected to with grafana for general software, network alerts (new devices connecting to network, suspicious DNS requests, suspicious ports, suspicious countries being reached out to like china, etc) or hardware failures (like a raid drive failing)… So yeah, automate if you know how to script or program, and you’ll be pretty much worry free most of the time.