Though extremely difficult to find, I request that you seek out this webpage for the BM818 manual:
https://fccid.io/2AON8-BM818/Users-Manual/BM818-Coperation-manual-V1-4-4107101.
Even here there is no clear documentation of the QMI.
HOWEVER if you go to:
https://lkml.org/lkml/2019/7/24/605
There you will see that the site says: “The BroadMobi BM818 M.2 card uses the QMI protocol”.
Broadmi is likely licensing an older Qualcomm chip.
The situation of problems only accrues if going from a different manufacturer, such as the MBIM device of Gemalto and seek to swap it for the BMI without a reload. Please do note this is not that I know, but what I can ‘dope out’ from the meager literature that I have at hand.