A little off topic, but if you are going with mostly managed services and you don't use k8s, what would you do to have decent tracing and observability? I'm currently using a combination of FaaS and cloud queues, for example.
Have you looked into instrumenting zipkin or opentracing? I instrumented zipkin in a Java project and found it generally pretty easy
You can check out DataDog or NewRelic - they do a decent job if you are looking for SaaS. If you are looking for open source products - checkout SigNoz (https://github.com/signoz/signoz)
Disclaimer: I am one of the maintainers of SigNoz