Monitoring

VictoriaMetrics / Prometheus

Reads up from a VictoriaMetrics or Prometheus API: a host is down when every target that belongs to it is down. CPU and memory widgets on host pages.

Beszel

Host status, CPU, memory and disk from Beszel agents. Adds hosts as systems (plan/apply) and installs the agent over Ansible.

Uptime Kuma

Plans a monitor per service that has a link and reads host and service status back. Needs the uptimekuma extra (in the image).

Certificates

Checks the TLS certificate of every https service (and endpoints you list): days left, issuer, names; warns before expiry and notifies.

Status from any of these shows as live dots on Hosts and in the sidebar, on the Services page, and as host.down / host.up notifications.