I am re-purposing an RB411U as a backup internet. Since 3G is too slow, I want to use an LTE modem. I did some research and I've found that the Quectel EC25-V is a good option, however, the device does not show up on the RouterBoard at all. There is nothing under USB, Port List, or PCI. I've also set the firmware to Ignore DirectIP Modem.
I've verified that the card does work in a laptop.