Stupid question: What open source solution can give me an easy Datadog(ish) experience and is simple to implement?
You should check out SigNoz (https://github.com/SigNoz/signoz) - It's an open source alternative to DataDog with metrics, traces and logs in a single application. You can just self host it yourself or try the hosted version.
PS: I am one of the maintainers at SigNoz