Ubuntu 18.04LTS, VPN split tunneling Transmission

[divStar]

Hello there,

I am having some serious trouble to get a working split tunnel set up for my Ubuntu 18.04LTS server.

I want to route Transmission's traffic via VPN while keeping everything else non-VPN (for now).

What I use:

• namespaced-openvpn
• PrivateVPN-provider
• Transmission 2.9.2
  

What works:

• Starting namespaced-openvpn manually using the following command:
  sudo ./namespaced-openvpn --namespace vpn --config /etc/openvpn/privatevpn.config.ovpn
• This results in openvpn asking for credentials and upon authentication and authorization it enables me to run the following successfully, returning the proper results:
  sudo ip netns exec vpn curl ipinfo.io
• What I do not know here is where the DNS resolution comes from. However: once I stop namespaced-openvpn, the second command claims not to be able to resolve "ipinfo.io"
• Running e.g. FireFox or cURL and apparently being recognized as an IP from somewhere in the world (not my own)
  

What does not work:

• Transmission; it might be working, but since I cannot connect to it using the web UI or transmission-remote-cli, I cannot check it for sure
• automated start of namespaced-openvpn-command above
• not sure what happens if the connection drops
• not sure about possible DNS leaks
  

In the vpn-namespace, only tun0 and lp are present.

Does anyone happen to have an advice on how to configure Transmission in a way that I could run it at least manually and have access to it (to see progress, add new torrents etc.)?

I have checked various solutions - especially a script for PIA, but apparently I cannot adjust it properly so it works for my case.

I am on Ubuntu 18.04 LTS. Any help is greatly appreciated.

P.s.: I am a software developer and I usually know my way around Windows, but I have had Ubuntu on my server for a few years now, so I am learning it, too. Though I am by no means a Linux professional (sadly).