Turris Omnia LTE Question

Can the optional LTE modem for the Turris Omnia be used as the primary internet connection from my wireless internet provider rather than via a wired ethernet cable?

My wireless ISP provides its own modem/router with an antenna and SIM card. ISP said their modem/router had no proprietary software and that if Turris Omnia could support LTE and the ISP-issued AT&T SIM Card, I might be able to replace their modem/router with the Turris Omnia and their antenna.

Lastly, where can I find a list of compatible/reliable LTE Modem cards that I can install in my Turris Omnia?

In case it matters, I’ve just re-flashed my Turris Omnia (1.3/1GB version) to latest 4.0 OS.