That's a change from what was asked which was isolation between each.
Yes, if they need to talk, share namespaces.
If you don't want a generic but true answer, don't ask a generic question and then be upset when the responses don't have enough detail about your specific situation that you hadn't described :-)
If you need more / different isolation, you're going to need custom nftables/ebtables rules.
In another model you could drop each bridge onto a unique vlan, and firewall them.
There's tons of options out there.
Anyway, if you had more specifics to go off of, there's plenty of network engineers and kubernetes/docker admins floating around willing to help - maybe start a Ask HN post?
You're still offering suggestions I said I didn't ask for. I'm sure you're trying to help, but at this point you're coming across as passive-aggressive.
Yes, if they need to talk, share namespaces.
If you don't want a generic but true answer, don't ask a generic question and then be upset when the responses don't have enough detail about your specific situation that you hadn't described :-)