I have exactly the same problem like the user khofm asked in https://unix.stackexchange.com/a/352968/394150
So in summary:
The openVPN client and the openVPN server instance work fine as long as I don't run them simultaneously. As soon as the openVPN client has a connection to the Paid VPN provider (in my case NordVPN), the WAN clients are unable to connect to the openVPN server.
My system is a Raspberry Pi 4 with dietpi (Debian Buster).
I'm very new to this community and this is my first question, therefore I can't add a comment on khofm question. My understanding of networks (especially about routes) is not very good, therefore I would like to know from khofm if he could explain his working setup in more detail with some explanations.
How does the OpenVPN server.conf looks, how about the client.ovpn of the Paid VPN Provider?
How do you separate the OpenVPN Server and OpenVPN Client in tun0 and tun1 with the two different subnets?
With the provided solution I could not solve my problem, maybe because I don't understand it that good. I wasted already serveral hours without any success. And I don't want to give up especially if I know that there is a solution. Please help me!
Thanks a lot in advance!