In AirVPN:
Navigate to Forwarded ports - AirVPN and login to your AirVPN account.
Scroll down to the “Suggest a range of sequential free ports” and press the “View the Graph” button. The first graph you see will all be in Pool 1 and will be mostly RED, Pool 2 will be further down and will be mostly GREEN. We are looking for GREEN ports in Pool 1. Now, find an open port in Pool 1 between the range of 20,000 and 50,000. Once you have done so, exit the graph and create a new port forwarding rule with that open port with P2P enabled (in Pool :1 of course). Once you have done so, navigate to your newly forwarded port rule, and set the “Local Port” to 32400 (This is the local listening port for Plex).
So, at this point we now have our new port forwarded port in pool 1 which will be our Public/External port and its traffic is being sent to our Private/Local/Internal port of 32400
For the next step, which may be optional but I have it and it is working with this applied, we will want to grab our VPN’s private IP address for our device and our new public port. To do this, we remain on the same port forwarding client page in AirVPN. We then go to our newly forwarded port rule and press the “Test Open” button. We don’t care how these tests turn out, we just want the IP. The IP we are looking for it our IPv4 layer IP (first row) and we are looking for the IPv4 address that is designated to our device. This will be the box that has a little person in it. Once you have found it, copy it and paste it in a notepad somewhere. Once you have it add an https:// to the front of it and then save that for Plex section.
Example: xx.xxx.xxx.xxx:32400 → https://xx.xxx.xxx.xxx:32400
In Plex:
Navigate to Settings → Network and scroll down towards the bottom looking for an input field labeled “Custom server access URLs”. In this field go ahead and paste in that https://xx.xxx.xxx.xxx:32400 link we just created. Once you have entered it scroll to the bottom and hit “Save Changes”
Now, navigate to Settings → Remote Access. Enable Remote Access if it isn’t already enabled, then enable the “Manually specify public port” checkbox. This will allow you to enter in that newly created public port from our AirVPN client area.
For example, if you made a P2P Pool 1 Public port of 24719 then go ahead and enter that in the box.
Now hit the apply button and you should be all set!
REMINDER: Doing it this way instead of split tunneling will require you to have your VPN on in order for your Plex Media Server to be accessible. You MAY be able to create a Port Forwarding rule in your router to resolve this issue, but I have not tried it.