Buy TP-Link AC750 Wifi extender
Go into WPS mode on the hotspot and start WPS and press the WPS button on the extender. Once connected, run a hardwire from the extender to the modem.
Now your hotspot is providing internet to your router
But I think the Soho has Wifi As Wan which will prevent the need for any wires or accessories.
I don’t know about over USB, but I’ve had an AT&T Nighthawk plugged into my BalanceOne WAN1 port via ethernet for a couple of years now and it works great.
I’m the op. I just got the M1 & my AT&T SIM Card & account yesterday, and all I can say is WOW. I know this is not all the M1, but replacing VZW and either a 5501L or 7730L even with those on MiMo antennas
What used to take me 3-4 hours to download and install an update to my Garmin Nuvi, now takes less than an hour–and this is a weekday vs the weekend.
The M1 tethers & charges nicely. I can disable WiFi if we don’t need it. It also has Ethernet–not sure what speed, the spec doesn’t say.
With the latest firmware update–it will run tethered without the battery installed. Over the years folks who leave their puks plugged in, with from a router or wall wart risk the battery swelling, and maybe worse stuff. No problem with the m1–doesn’t need a battery.