As karel indicated, this already is done for you - right under the question's title is a box where it shows the link to the duplicate.
In the mobile app, this is along a bar/box at the bottom of the post window/screen. It says that the post is marked as a duplicate, and there's a nice little info button there that'll show you details of the duplicate and ...
In response to an answer to your only question asked on the main site, you wrote:
The two responses I have received here have convinced me that I am not a suitable member of this elitist club and I will retire graciously and apologise for taking up your valuable time
If you still feel that way, the simplest option would be to just not visit the site any ...
Have some image data in the clipboard and press ctrl+v while in the editor, click "Add Picture" and immediately, the image is in place.
For super-fast copy-pasting a screenshot with Ubuntu, copy-paste a shot from full screen (ctrl+print) or from a bounding box (ctrl+shift+print).