I have been able to run a VPN container called 'vpn' and connect all my other containers through it with these settings:
Extra Parameters: --network='container:vpn' Network Type: None
This has worked since I started to use unRaid 6 months ago or so.
Version: 6.7.3-rc4 works fine but 6.8.0 rc5 gives an error:
Error response from daemon: Container cannot be connected to network endpoints: container:vpn, none.
Has the docker version changed? Any ideas how to get this running again?