If you have the time to spare (a few weeks perhaps, if coming from zero) to experiment and read, Prometheus and Grafana offers a lot and can be really flexible. I use a pretty simple bash script that scrapes my desired https endpoints and writes out the results to a file Prometheus (node-exporter) understands, and from there I can write alert rules in Grafana to fire off notices by email or slack.
If you have the time to spare (a few weeks perhaps, if coming from zero) to experiment and read, Prometheus and Grafana offers a lot and can be really flexible. I use a pretty simple bash script that scrapes my desired https endpoints and writes out the results to a file Prometheus (node-exporter) understands, and from there I can write alert rules in Grafana to fire off notices by email or slack.