I think the only way to really do this on the CX LX2 would be installing a 5G NR modem into the PCIe x8 slot. Generally most the current consumer modems like the ones from Quectel are only in the m.2 form factor, so you would need a PCIe to m.2 adapter that works with the correct m.2 keying of the modem.
technically yes, but you would still most likely need an adapter and may run into physical interference issues for the modem card. Most wwan modems are B-key, which won’t mount directly into the M-key m.2 on our carrier.