You could for example just run one VM for all of your observability stuff, and stick these tools on it and store data to disk.
Alternatively, if you've got some money and you're systems are OK with outbound internet connections. SaaS monitoring solutions like NewRelic, Dynatrace, etc. are much more plug-and-play.
For logs, there’s Loki which is a lot saner choice than ELK in 2025.
To have proper troubleshooting abilities, you will need a bit more than tooling. You should also need to spend some time instrumenting your apps (Prometheus exporters can only take you to a certain level, e.g. node_exporter for host level stats, or other technology-specific exporters) with metrics, and ensure that your apps are logging in a structured way at least.
disclaimer: I'm a co-founder
I do like BetterStack heartbeats, but there is nothing similar for "pushing" a failure alert. You just push all your logs then configure filters in BetterStack logs.