I have to admit I'm not sure if the Software Manager shows different app lists dependent on the version of LM on the users machine. The official Shutter PPA wasn't maintained for quite a while so maybe it was dropped from the repository when LM 20 was released for those running that release. Maybe someone with more knowledge could confirm one way or other?
Either way, given the confirmation by JerryF that the official PPA is now actively maintained again I'd probably just install it using the instructions on the Shutter website:
Code: Select all
$ sudo add-apt-repository ppa:shutter/ppa $ sudo apt-get update $ sudo apt install shutter