Are you asking about instrumenting an opensource data driver library, so that when that library is used in applications that have enabled ApplicationInsights, telemetry from that data driver library shows up?
If this is the case, the library needs to be instrumented with DiagnosticSource/Activity, just like other libraries (eg: SqlClient, HttpClient), and then write a module like DependencyTelemetryModule to listen to the DiagnosticSource/Activity callbacks, and convert them to ApplicationInsights model.
Doc explaining the instrumentation side:
https://github.com/dotnet/runtime/blob/master/src/libraries/System.Diagnostics.DiagnosticSource/src/ActivityUserGuide.md
Actual code showing how HttpClient is intrumented:
https://github.com/dotnet/runtime/blob/master/src/libraries/System.Net.Http/src/System/Net/Http/DiagnosticsHandler.cs
(Disclaimer: I work in Application Insights team. And also as part of .NET/OpenTelemetry. There a fairly big shift in the guidance on how to instrument libraries. It still uses Activities, but in a different way. The new guidelines are not published anywhere officially, it'll be done by .NET 5 timeframe ~Nov 2020)
Is this what you were looking for?