Zabbix

Zabbix has been monitoring networks since before "observability" was a word: agent-based and agentless collection, SNMP for network gear, auto-discovery, templates for hundreds of device types, and a serious alerting engine with escalations.

It is a system you administer, not an app you run — expect a database to care for and a UI that values density over beauty. In exchange you get proven reliability at scales where trendier tools struggle.

The right tool when your "homelab" includes switches, UPSes and a rack, or when work asks for something battle-tested.