I have zero experience with soulseek but I'd connect it with https://github.com/qdm12/gluetun I also wouldn't route jellyfin (plex) through the vpn

Since you're running on Linux you don't need extra software like some suggested.

Systemd can be used to restrict a program networking to your VPN. The following is an example of how to it for Transmission and you can adapt it to any other service. It boils down to overriding the default daemon unit by using the following command:

systemctl edit transmission-daemon.service

Then type what you need to override:

[Service]
IPAddressDeny=any
IPAddressAllow=10.0.0.1 # --> your VPN IP here

Another systemd option, might be to restrict it to a single network interface:

[Service]
RestrictNetworkInterfaces=wg0 # --> your VPN interface

Save the file and run systemctl daemon-reload followed by systemctl restart transmission-daemon.service and it should be applied.

• https://www.ctrl.blog/entry/systemd-application-firewall.html
• https://www.freedesktop.org/software/systemd/man/latest/systemd.resource-control.html#Network%20Accounting%20and%20Control
• https://www.freedesktop.org/software/systemd/man/latest/systemd.resource-control.html#RestrictNetworkInterfaces

I just create a tun1 with openvpn (sudo openvpn --config yourConfigFile.ovpn ) and then set Nicotine to use it. Easy as...

nicotine+ has an option to bind to an interface