What's the status of FlexLayout compare to other layout options

I’m new to Spring Boot and Vaadin and I’m learning to use various components, first of course is understanding the value/use of the layout components.
I see a few old examples of FlexLayout but when I search to find documentation of features I can’t find anything (except javadoc stuff). Furthermore, Vaadin webpages enumerate other layouts in a number of places with
reasonably good feature overview and example snippets but FlexLayout is never listed. Has FlexLayout been overcome by other newer ones and are discouraged? If not where can I find better description of how it compares to
other layouts?

I’m sure some Vaadin folks will be able to clarify where FlexLayout sits in relation to the other layouts, but I can say for my needs I have only ever used VerticalLayout, HorizontalLayout, and once in awhile FormLayout. My layout needs may not be the most complex, but I would say that while you are starting out, it would be fine to focus on these basic layouts, since you can get very far with these alone, and as you mentioned, these are what you usually see in example code.

This video on the two main layouts (vertical and horizontal) gives some more information on their usage: https://www.youtube.com/watch?v=Efv_cPHEqdQ

Flex layout isn’t mentioned because it resembles the basic CSS flex layout. If you know how to use that, you can get a grip on this one. The methods matching the css properties you apply in a css based flex layout