I have just installed a Compex WLE600VX mini PCIe AC WiFi card into a MiFi and it is not showing up running lspci or lsusb. I am on a custom build of OpenWRT and i believe I have all the right drivers installed, a Sierra Wireless LTE card works in the slot and so too does a USB WiFi dongle plugged into the USB port.
The Compex card uses a mini PCIe 1.1 interface and does not appear to have USB signalling broken out, as per the card pinout and the data sheet.
Does the MiFi only support mini PCIe cards that have a USB bus?
The datasheet page one says you need the ath10k driver, so install that and see if it works?
All the sierra and quectel cards seem to be using USB though.
I have that driver installed, no joy. The driver won’t stop the physical card from showing in lspci or lsusb, for example.