I am. Mulesoft provided a sort of hack to get this working which includes using a mule-4-agent.jar file, that they provided, and modify the wrapper.conf file. It provides some decent functionality and monitoring capabilities. Mulesoft really needs to provide official support for this in their oneagent.
I'd be curious to know too.
It's a common problem with most enterprise services buses, and API gateways - that this middle tier will receive a HTTP call and start a new HTTP outgoing call to another tier. This makes it impossible to see end-to-end because the HTTP call is completely new. It'd be good if Mule could add something like W3C trace-context headers with the OpenTelemetry API. Then it'd make this easier.