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.)?
It’s bursty; I tend to do a lot of work on stuff when I do a hardware upgrade, but otherwise it’s set it and forget it for the most part. The only servers I pay any significant attention to in terms of frequent maintenance and security checks are the MTAs in the DMZ for my email. Nothing else is exposed to the internet for inbound traffic except a game server VM that’s segregated (credential-wise and network-wise) from everything else, so if it does get compromised it would be a very minimal danger to the rest of my network. Everything either has automated updates, or for servers I want more control over I manually update them when the mood strikes me or a big vulnerability that affects my software hits the news.
TL;DR If you averaged it over a year, I maybe spend 30-60 minutes a week on self hosting maintenance tasks for 4 physical servers and about 20 VM’s.