https://itsfoss.com/take-screenshot-linux/
I found this helpful webpage for various ways of taking screenshots, when using a Linux Distro.
I have an app called Screenshot. I think it was installed by default on Ubuntu. Has multiple options and works well.
Thanks Mike for the info about "Screenshot". I will have to look at that one and the one (Flameshot) that they mention in the article.
On my Mint 19.1 , Screenshot is installed by default. I didn't realize that there was a screenshot program, included with the Mint Distro.
Thanks for the link, Bill. Xubuntu comes with one installed, too. This little tip might only work with Ubuntu-based distros but you can try it. If you just need a full-screen screenshot, press the PrtScn button on your keyboard. It doesn't save it, it just brings up a pic of the desktop you can use. It's usually among the Home, End, PgUp, PgDn buttons, etc.
Looking forward to more screenshots from you, Bill! :)