Uptime kuma is a fantastic self hosted monitoring tool. One docker run command and you are up and running. Once you are in you have full control over checking status of urls, frequency, allowed timeouts, and a HUGE list of notification providers
docker run -d --restart=always -p 3001:3001 -v uptime-kuma:/app/data --name uptime-kuma louislam/uptime-kuma:1
I deployed it in my homelab today.