My favorite screenshot capture software are Flameshot and Shutter. The latter hasn't had an active development in years, but I like to mention both of them because sometimes I simply can't actively choose between the two depending on the distro I'm using—for instance, Flameshot fails to launch on Pop!_OS 18.04 (a Ubuntu-based distribution) without some intense troubleshooting while Shutter does it successfully (and smoothly); they both fail to launch on Fedora 31 (which is the reason why I ended up abandoning the idea of having it as my main distro), but work fine on Manjaro (which is based on Arch Linux).
But why such software is so important to me to the point of making me give up on whole distributions? Besides offering an easy way to capture both the whole screen and portions of it, they also offer basic edit tools relevant for technical writers such as colorful arrows and boxes, blurring and pixelating. Shutter even offers options for selecting a single menu or cascading menus and capturing tooltips!
Flameshot works perfectly out of the box. However, the editing tool for Shutter needs a few additional packages to GooCanvas, a canvas widget for GTK+, to work. They should be installed in the following order:
libgoocanvas-common(translations)libgoocanvas3(shared library)libgoo-canvas-perl(Perl interface)
Once you installed all of them, kill all running instances of Shutter (using the killall shutter command) and launch it again. The Edit option should become available as soon as you capture a new screenshot!