I read that was highly recommend, and looked closer into the config options for transmission torrent client on Debian. I don’t see any options in that regard. Where can I find instructions?
I know you’re asking about transmission, but… Qbittorrent has an option in the GUI that allows you to specify what network interface it uses to communicate through. Therefore if your VPN isn’t up, it won’t use your normal network. And if your VPN drops out, it also won’t use your normal network. Just another option in case you’re interested.