Here is a thread regarding this issue you can review. Currently the only lack of functionality I'm seeing is if there are two local networks Veeam doesn't seem to be able to identify which NEA to spin up on the tenant side to facilitate L2 connectivity during a partial site failover.cloud-connect-replication-f45/partial-failover-for-linux-vm-s-t36930.html
With regards to your question about failover plans, I've had success in the past manually typing an IP address in for the NEA rules. Do other rules seem to work that have IP's that are able to be recognized by Veeam? During the failover are you able to log in to the Linux VM and ping the gateway? Internet? You can also review the logs of the NEA to determine what rules have been applied and see if there are any issues there.