TYPO3 v11: Double content in backend module template

Problem: When registering a module as submodule of "Web > Info" (3rd level), then content was duplicated - the header was shown twice, the content was shown twice.

Solution: Only return the content that shall be rendered after the docheader, not the docheader itself. Do not render the moduleTemplate yourself. Use a StandaloneView.

Keywords:

• typo3 backend moduletemplate duplicate content
• typo3 backend moduletemplate double content
• typo3 backend template doppelt