You can easily look for duplicates by:
📡 Going to the following website:
https://bugs.launchpad.net/ubuntu/+source/[DESIRED PACKAGE'S NAME]/+bugs?field.status%3Alist=TRIAGED&field.status%3Alist=INPROGRESS&field.status%3Alist=FIXCOMMITTED
🔍 Then, by using the search functionality of your web-browser (by pressing the "Ctrl+F" key combination), looking for bugs with similar importance and title.
Duplicated bugs are those which describe exactly the same issue:
💣 Same cause.
🐾 Same steps to reproduce.
🔥 Same consequence.
When having to choose which duplicate to retain:
💟 Keep the one which is more descriptive.
🎁 Triage it as far as possible.