Alternatively a server-only qBittorrent (controllable via the web-interface only) without docker (package: qbittorrent_nox) behind an always on VPN, configured to only bind to the network interface of the VPN so that it doesn’t send any data outside the VPN does the same but it’s much lighter so you can put it in shitty-shit hardware.

This is what I have in the cheap mini-PC which I use as Homeserver/NAS/TV Media Player.