There is no option at all. And I took a moment to try to get anything. I only get a squared video player, but the video itself is still rounded. There are just black pixels added to make the video squared.
Answer: I cannot "set the layout to anything else" because, as I said, I have NO OPTION AT ALL. Nothing to configure the extension.
You must have the layout set to "Disabled", where the video player is not supposed to be squared (the black pixels around the player is actually a bug, the whole thing is supposed to remain rounded). Try setting the layout to anything else (2021 is the closest to the current layout), and the video should be squared.
Edit: To change settings, pin the extension to the toolbar, then click on the icon to make the config window pop up. Here's how you do that: https://imgur.com/a/IIxddDa
