There is no problem at least connecting M1 to WAN port over Ethernet cable and LTE hotspot to WWAN over wifi repeater at the same time. It “should” also be feasible to connect Nord 10 over USB tethering, although I have not tried it myself.
The priority order is configured in the /etc/config/mwan3 file, with WAN, then WWAN, then Tethering:
There may be time delays between switching over from one connection to another connection.
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