Fibocom L850-GL works in LMDE 3 Cindy in Clevo P651SA (motherboard P65_P67SA).
PCIe interface in the M2 LTE slot is not supported in this laptop, therefore the modem automatically works with the USB 3.0 interface that his modem also supports on Linux.
Mind you, this is a laptop from 2014 (year of launch) or rather 2015 (when the laptop was sold with LTE antenna on board from different OEMs around the world).
This modem was designed to be a transitional modem for laptops that had no PCIe support in the M2 LTE interface slot.
From 2016 laptops had PCIe support in the M2 interface (connection slot).
These newer laptops need the newer modem Fibocom L860-GL to work on Linux, as they came with PCIe interface support only.
The older Fibocom L830-EB that came with USB 2.0 support only, will also work in Linux on any laptop that have the M2 interface, that being older or newer laptops.
Hope this helps :)