Why isn't there an official XML Schema for XHTML5?

Question

Accorting to this article, there are 2 flavors of HTML5: html and XML.
On W3 I can't find an official DTD or XML Schema. On the internet I only found unofficial ones.

So, how can I validate an XHTML5 document?

Answer 1

Re:

Why isn't there an official XML Schema for XHTML5?

See this comment on the v.Nu GitHub repo.

For further reading, see the unsoup/validator GitHub repo.

Re:

how can I validate an XHTML5 document?

Upload an XHTML5 document with the file extension .xhtml to an instance of the Nu Html Checker (v.Nu). For example:

https://html5.validator.nu/

To validate XHTML5 as you type ("on the fly"), consider using the Atom editor with the new linter-vnu package (published today).