Have Shutter on my system for many years. Recently upgraded to 23.04 and now I find that Shutter won’t open. I’ve tried reinstalling it from Ubuntu Software which it does without protest but it won’t open. Then I read your article and tried to download the Universe repository but that is not allowed:
The repository ‘Index of /linuxuprising/shutter/ubuntu lunar Release’ does not have a Release file!
Is this something to do with the change to Snap packages?