My understanding is that when you flash your tune on a 68RFE-equipped truck, the Clutch Volume Index values (CVI) are zeroed out.

The quick learn process with a scan tool programs in calculated CVI values, and then the drive learn cycle refines the CVI values as the transmission adapts.

Hopefully, others more knowledgeable about the 68RFE will chime in and correct me if this is not the case.

You can use your OBDLink MX+ with AlfaOBD software.

I just checked, and the RFE quick learn is listed for Diesel Cummins: MY2013+, so it should work on your 2021, but I am unable to confirm.

https://www.alfaobd.com/index.html