Used to not monitor at all, but after setting up crowdsec I got completeky into prometheus + grafana system resource and security monitiring on my dedicated hetzner server.
I also keep uptime kuma on another cheap vps to monitor the states of websites directly for issues and I have seted up watchtower to send ntfy notifications on updates so I can know an update is the one fucking everything up.
Recently also setup restuc backups so I made it so I also get backup health check logs as ntfy notifications on my phone, which really helps me keep everything runnig.
What I really need to also do is create prometheus/grafana alerts for additional things to get notifications on my phone for them also ( like when crowdsec starts to randomly not get any more acqusitions, so I have to restart it. Once passed over a week before I looked at grafana and caught that ).
Note: this is all a hoby, I also don't host anything at home out of a couple reasons, most important being internet and hardware is expensive af here so it's simply cheaper for me to play around with vps's and hetzner dedicated servers.