Stopping the "New Microsoft Edge" Nag (Firefox)

I was in the middle of doing something tricky this morning and suddenly this Edge screen opened (full screen) with no close button, interrupting my thoughts. No close button and when I right clicked on the tool bar icon and clicked on close window, nothing happened. Eventually, I had to begin their tutorial and then a close window appeared and I closed it and could back to work.

If MS thinks this is the way to make friends and influence people they got another think coming. I said to my wife, if only my text editor could only be made to work in Linux, I would go through the effort to learn how to use it. I once tried to use a Windows simulator in some version of Unix, but the editor just did not work properly.