Stuck with GL-MT300N-V2 Wireless bridging/routing

After a week of fiddling have to admit defeat. From the illustration: Network A with GL-MT300N and the latest stock firmware is working fine so is Network B on its own. What are my options in routing/bridging A and B with full bi-directional traffic? I can sacrifice Network A local DHCP server. Tried bridging via WDS - lost tethered Internet. Routing with “relayd” worked only one way - from A to B. Any hints? Can that be done with GL-MT300N or do I need additional bridge/router? Thanks in advance.


Do you want to exchange visits between A and B?
Is the network B connected to 300n-v2 via WIFI?
Can you configure the firewall of B network?

Both A and B are on the same physical location. Network B is essentially a single non configurable WiFi device with AP at (it’s a Furuno Wireless Radar ). See stock image below. The device only works with its client iOS application within the same IP range ( GL-MT300N can bridge Network A to Network B via WDS, but then I lose Internet.