You are probably seeing this because you wonder where did all the Themes go.
We have taken down the Themes and converted some of them to collections. We have otherwise introduced the new concept called Collections which will have various layouts. You will see the list of all the collections when you want to add the next scene.
You could either choose the 'Blank Template' scene or go with a collection of scenes. There is a whole set preset when you click on 'See all'.