Hi Andrew,
As I understand it your router has an 'inside' which deals with YOUR wifi and Ethernet links ie supporting a LAN,
And an 'outside' which deals with however you connect to the internet (via 5G or the ISP's cables) ie connecting to the WAN.
Thus while a 5G router may be different from an ISP's router, on the "inside" they should be identical, your B2 will not care which type of Router it is connecting to.
Fred