The Submenu block looks (sounds) quite OK in the Long and Short "full width" versions. 
Choosing a numbered list in some of the levels makes it a bit too verbose (it announces the list, then the list number for each element...), but it's correct in terms of a11y.

The Sidebar version has a few caveats. It is browsable, but it's read before the content when it's present, not sure this is the behavior we want. It's not a big deal, but maybe it's worth a UX look into it.

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