Sometimes, when making a tutorial or when wanting to send feedback to a company, you may need to take a screenshot of a dropdown menu. But when you press the PrtScn key, the menu disappears. Fortunately, there are some ways to take the screenshot. The trick is simply to invoke the screenshot application by setting an interval of a few seconds during which you open the menu and keep it ready to be "screenshotted".
Shutter:
Shutter used to be available on Ubuntu via apt, but from Ubuntu 20 onward, it's available via snap. So to install it, use either:
sudo apt-get install shutter
or
snap install shutter
Once you install and start Shutter, just open up the preferences and select the option to capture the screenshot after a delay of x seconds.
Once you capture a screenshot, Shutter also allows you to edit the image within Shutter itself. You can crop it, add arrows and do a lot more. So there's no need of opening a separate application like Gimp.
Shutter also offers options to automatically upload images to various servers you choose. Truly a versatile tool!