https://online-it.nu/install-transmission-torrent-client-ubuntu-18-04-bionic-beaver/

https://www.maketecheasier.com/how-to-download-torrents-from-the-command-line-in-ubuntu/

$ sudo apt install transmission-cli transmission-common transmission-daemon

// but I don't want transmission-daemon
$ sudo systemctl stop transmission-daemon

// can download with a command
$ transmission-cli xxx.torrent -w ~/Downloads

// to re-download,
$ rm ~/.config/transmission/resume/*.resume
// and need to move old torrent to a new directory (?)