Gatus is a developer-oriented health dashboard that gives you the ability to monitor your self-hosted services and websites using HTTP, ICMP, TCP, and even DNS queries as well as evaluate the result of said queries by using a list of conditions on values like the status code, the response time, the certificate expiration, the body and many others. The icing on top of the cake is that each of these health checks can be paired with alerting via Slack, Teams, PagerDuty, Discord, Twilio and many more.

https://technotim.live/posts/gatus-uptime-monitoring/
Gatus plugin for Homepage