Actually I was a bit optimistic here :
The Mod seems to be changing its presented MAC address after each reboot. That confuses NetworkManager which thinks it is a new connection and therefore doesn’t apply rule for setting the DNS.
I ended up listing usb0 in /etc/network/interfaces so that NetworkManager leaves it alone, and adding
supersede domain-name-servers 192.168.0.1
to dhclient.conf so that DHCP does not change /etc/resolv.conf when plugging in the Mod.
Seems to work now, even after computer or mod successive reboots