Ubuntu – Cannot use screen capture apps in Wayland

On recent versions of Firefox, there is no need for any plugins. This capability is built into the browser.

1. In Firefox, use Ctrl+Shift+F2 to open the Web Developer Console.
2. Type :screenshot --fullpage (this will autocomplete, so :s Tab --fullpage will work).

That will save the screenshot as a PNG file to your downloads folder. By default, the filename includes the date and time. You can use a different filename if you wish, simply by passing it in on the CLI: :screenshot --fullpage my_name.png.

This will also work on pop-up windows, but each window will need to be saved individually. I know of no way to combine them into a single screenshot. (You could, of course, do that in GIMP or another image-editing tool later.)

I realized, after some search and time, that Xorg wasn't even installed on my laptop, possibly after upgrading to 17.10, when Wayland took place over after that. That said, I managed to install Xorg using sudo apt-get install xserver-xorg --install-suggest. Thus, both "Ubuntu on Xorg" and "Unity" options got to work, although Unity gets slow for some reason not yet identified.