In Ubuntu MATE 20.04, which is what I use, provides the screenshot tool in the menus and, yes, it only saves in .png, but these are some of the default keyboard shortcuts you might find useful:
- PrtScr Takes a screenshot of the entire screen.
- Alt+PrtScr Takes a screenshot of the window which is active.
- Shift+PrtScr Takes a screenshot of the rectangular area you select.
You can use the Keyboard Shortcuts Preferences tool to modify the default shortcut keys if you would like to use different shortcuts.
By the way, SCROT has been obsolete for years. It's successor is a package called Shutter, which I used for years. It's last bug fix release was in 2018, but that doesn't mean it's bad. In fact, you might consider installing it from the snap repository. https://snapcraft.io/shutter If you want to install it from a terminal, you can use the command
sudo snap install shutter
For more information on different ways to find and install software packages, see this: https://guide.ubuntu-mate.org/#applications-software