My Librem 5 does not recognize this card. lsusb does not list it. I tried in the slot dedicated to the Wi-Fi card as well as, for testing only, in the slot dedicated to the cellular card. I conclude that the tested card requires PCIe and does not support SDIO or USB. In a laptop, lspci lists this card.
Per a Purism publication, they chose SDIO and USB because they are “defined interfaces” allowing to separate CPU from the WiFi, Bluetooth and cellular modems to prevent them from accessing the RAM. So, the reason why the PCIe is absent in Librem 5 is because it is more difficult to secure from a hostile peripheral.
A card of that form factor sits as firmly in the slot as the full-sized. It is exactly the right width to be held by the left and the middle plastic holders along the edge.
The slots do not allow to secure cards with screws. As a side note, when disconnecting the antenna, one should hold the card in place to avoid popping it out suddenly with the antenna still attached. When removing or inserting the cellular card, the wires need to be held in grooves in the sides.
Here is how the cards look.
The back side.
The card installed.
The side view showing the plastic holder.
The card in the cellular slot. It cannot be secured in place. The wires are too short to reach, so I connected AUX antenna to MAIN on the card to have at least one.
