I use some batch scripts in my proxmox installation. They are in cron.hourly and daily checking for virus and ram/CPU load of my LXC containers. An email is send on condition.
What are your tipps or solution without unnecessary load on disc io or CPU time. Lets keep it simple.
I use netdata, it’s very good at digesting thousands of metrics to sharing actionable. The cloud portion is proprietary, but you can toggle off the data collection. I did turn on the cloud portion though, I get email notifications when something breaks. Might sound counter to the self hosted mantra, but a self hosted monitoring system isn’t very helpful when your own systems go down.