If you look at libraries like OpenTelemetryOban you can see that the common pattern is to create :telemetry hooks that then initiate open telemetry spans. This allows you to stick with the more general purpose telemetry library while also enabling people who use open telemetry to get otel spans out.

You got me wrong. I am not suggesting writing telemetry in otel always. I am suggesting to have a relay which automatically converts all telemetry spans to otel spans, and as far as I can see, there are no limitations for this, but still, every opentelemetry_* library writes this boilerplate from scratch

I thought so too, but it turns out that telemetry.span generates unique span context in metadata for every span, so it is possible to convert a telemetry span to opentelemetry span.