Breaking: #72492 - Removed XHTML2 support 

See forge#72492

Description 

The support for XHTML2 documents in the TYPO3 Frontend has been removed.

Impact 

The TypoScript option config.doctype = xhtml_2 has no effect anymore.

Affected Installations 

Any TYPO3 instance using XHTML2 for frontend rendering.

Migration 

Disable all header code and set your own doctype.