This script will add all torrents from an http://ultrastar-es.org RSS feed to transmission, using its RPC interface.
The simplest invocation is
ULTRASTAR_RSS="<your rss url here>" ultrastar
or, if you want these torrents to be added to a specific folder different from your default transmission folder,
ULTRASTAR_RSS="<your rss url here>" ULTRASTAR_TARGET="$HOME/Music/Ultrastar" ultrastar
go get -u git.sr.ht/~vicentereyes/ultrastar
If you get a connection refused error, it's probably because transmission isn't running, or because it doesn't have remote access enabled. Go to Edit->Preferences->Remote->Allow remote access and leave the rest as default.