I seem to remember that maybe it was in Chrome or somewhere else that one could right-click on a web page and get a full screenshot of the entirety of the page as though it would fit on the monitor properly without zooming out. With Firefox though I have found no such feature, I am running Arch Linux with GNOME 3.24.2 and Wayland, is there any way to do this? Maybe a Firefox add-on or some software?
You can do this with Firefox' Developer Tools as described at the Mozilla Wiki:
* Open the Developer Tools (Hamburger Menu -> Developer -> Toggle Tools) * visit the Settings page * find the section labeled "Available Toolbox Buttons" * check the box labeled "Take a screenshot of the entire page"
Youcan now use the Screenshot button (a small camera) in the upper right of the Developer Tools to take a screenshot of any website.
I would generally advice you to just try googling first. It's quite a trivial thing to find without asking it on U&L SE. And moreover it's not a *nix specific question.
But still, here you go: ScreenGrub
This addon is what you were searching for.