OneUptime (https://github.com/oneuptime/oneuptime) is the open-source alternative to DataDog. It's 100% free and you can self-host it on your VM / server / cloud or you can use SaaS at https://oneuptime.com<p>NEW UPDATES (since we last posted to HN): We now support OpenTelemetry (https://opentelemetry.io/) natively which will help you to monitor, observe and debug any app, service, database or stack.
Random landing page feedback: maybe a simpler H1 text looks better: <a href="https://s3.amazonaws.com/i.snag.gy/p5kvVG.jpg" rel="nofollow">https://s3.amazonaws.com/i.snag.gy/p5kvVG.jpg</a>