My RBM33G + LTE card is configured with an IP Passthrough. In other words, the router is somewhere else and the RBM33G acts as simple modem.
The problem is that in such a configuration RouterOS doesn’t seem to have internet connectivity.
How do I give internet connectivity to the RouterOS without breaking the IP passthrough?
You can attach VLAN interfaces to the Ethernet interfaces you use to connect the two routers together and create an interconnect subnet in that VLAN, so that the RBM33G could talk to the world via the other router. Of course that requires enough flexibility on the other router.