Lots of options here TBH and I haven’t put much thought into it. Providing a service by running and managing software updates, migrations etc…, is one. MongoDB Atlas and Confluent Cloud are good examples of what I had in mind.
Why do people hate the “as a service” model?
If you don’t mind the runtime overhead OpenTelemetry would do the job (with maybe some sort of manual instrumentation for things like timers) and builds a service map.
IMO however if your services are closely tied together then how about grouping them together into one or multiple mono-repositories ? Or at least start designing your bounded contexts so that documenting by hand doesn’t become a maintenance burden.