How do I find torrents which are no longer registered on the tracker?
Solution 1:
The client I'm using is qBittorrent, which has a Tracker column that can be displayed by right-clicking the column headers and placing a check-mark next to "Tracker". The Tracker column is empty when there are no trackers, and can also be sorted by value so as to bring together all the blank fields, for easy delete.
I don't use Transmission, but perhaps it has a similar column.
If it does not, then other Transmission interfaces might include this data: Shift or Transmission Remote GUI.