I'm looking to imitate ShareX's behaviour in Gnome. I want the screen to freeze before I take a regional screenshot. It would also be nice to get other features of ShareX too, however, I'm not sure if that's easily achievable.
A little late to the party, but switching from windows I missed that feature a lot. I just recently discovered flameshot which does exactly that (with additional features like making some small edits on the fly).
You can install it via:
sudo apt install flameshot
and then invoking it on the command line via
However, that seemed annoying to me so I also created a shortcut with the print button (you need to disable the standard screenshot first though). See Ubuntu 18 how to change screenshot application to Flameshot?