Downloading Ubuntu ISO images with a torrent client is one of the most efficient ways to obtain the installation media. Torrenting allows you download the file from multiple sources simultaneously, which means you'll wind up with a very speedy download because the entirety of your network's download bandwidth can remain saturated. It's a very reliable method for downloading large files.
This is a companion discussion topic for the original entry at https://linuxconfig.org/ubuntu-torrent-download