Very minimal. Mostly just run updates every now and then and fix what breaks which is relatively rare. The Docker stacks in particular are quite painless.
Couple websites, Lemmy, Matrix, a whole email stack, DNS, IRC bouncer, NextCloud, WireGuard, Jitsi, a Minecraft server and I believe that's about it?
I'm a DevOps engineer at work, managing 2k+ VMs that I can more than keep up with. I'd say it varies more with experience and how it's set up than how much you manage. When you use Ansible and Terraform and Kubernetes, the count of servers and services isn't really important. One, five, ten, a thousand servers, it matters very little since you just run Ansible on them and 5 minutes later it's all up and running. I don't use that for my own servers out of laziness but still, I set most of that stuff 10 years ago and it's still happily humming along just fine.