Skitch needs to be screen recording permission, but it's not showing up in Screen Recording apps for your Mac user.
I fixed like this:
Log in as another admin user on your Mac. You might need to make one.
Launch Skitch and take a screenshot.
Now you should be able to give screen recording permission.
This permission will automatically show for your primary user, too.
Hope that helps!
If you double click a note, you will get an Evernote window with no list ("Open Note in New Window") . This window will spawn new windows if you use CMD-J, so it's a far cry from what you want, but it might be useful.