IP Addressing in Bridged Mode with VLANs?

I'm evaluating Sophos XG in a virtual environment with a bridged configuration, an interface br0, with one physical port attached to a router and the other attached to the core switch.

100% of the traffic between the router and switch is 802.1q-tagged, including VLAN 1 which I use for management, there is no untagged traffic.  First question - is VLAN 1 special in any way for Sophos XG?  We've been discussing changing that VLAN ID because it's not consistent across all vendors.

So having said that, I'd like to assign an IP address to the device on the management VLAN.  I've tried a number of ways of configuring this but no matter what, I cannot access the device from systems outside that management VLAN - even after adding static routes and "allow all" firewall rules on it.  The only way I can get into it is from systems on the same VLAN.

What am I missing?