

If it was Windows, it would simply be a matter of configuring the Split-tunneling options in the mullvad app and it would work the way you want, but on to use the split tunneling feature in mullvad on linux is a bit clunky and doesn’t remember your settings so it annoyingly needs you to manually whitelist each app everytime you load it up.
What I do is I run mullvad in a gluetun docker container on my nas and have the environment variable “HTTPPROXY=on” set.
Then, I connect apps on my desktop computer to gluetun by going into the network settings of whatever app I want to route through mullvad and set the proxy settings to “HTTP proxy” <nas ip>:8888. I use these proxy settings for things like FreeTube and one of the web browsers i have installed that I want to use only with a vpn.
This will work if you set the http proxy setting in qbit, but if you are going to the trouble of setting up docker, you may as well have qbit running in a docker container too.
Maybe the best option for you is to install docker (even if you don’t have a server or nas, you can run it on your desktop), and run gluetun and qbit in docker containers, this will auto start on boot running headless in the background and the vpn wont interfere with the rest on you computer.
Wow, that’s crazy. Could really get creative with your config using that!