Hello,
Netbird is currently not available on Teltonika devices.
An alternative to VPN Hub could be ZeroTier, a configuration example for which is available on our Wiki here. While it is not a self-hosted solution, it does allow you to connect up to 25 nodes with a free tier. The main advantage of ZeroTier is that, unlike most other VPN services, it does not require a public IP address on either end of the communication. It supports pushing routes to the clients, so a very minimal setup is needed, and the LAN networks of the devices can be reached.
If you are using a private network, then any of the VPN services offered on RutOS should be suitable for your solution.
It should be mentioned, that we do offer On-premise RMS installations, however, it is a paid service and is oriented towards businesses. If this is something that interests you, please fill out the "Choose your own" form here.
Let me know if any additional information is needed!
Best regards,
DaumantasG