In my experience, it just worked -- I was at an org that ran 3rd party java services alongside our normal array of microservices (that all used our internal instrumentation library that wrapped OTEL) and using the OTEL autoinstrumentation for those 3rd party services was pretty trivial to get setup and running (just wrap the command to run the app with the OTEL wrapper, hand it a collector url.) Granted -- we already had invested in OTEL elsewhere and were familiar with many of the situations in which it didn't just work.