I’m not sure about containers, but in Qbittorrent, Settings, Advanced, there is a “Network Interface” setting you can use to force qbit to only use a particular network interface. My VPN has it’s own network interface, so if it drops out, qbittorrent just stops downloading until the VPN comes back up. So, no IP leaks. Hopefully this helps you out a bit!
Link qBittorent docker container to VPN
I’m trying to link a docker container qFlood to my VPN (proton) on the host to prevent IP leaks....