TYPO3 Core

I am curious, how do you create a new doktype via Extbase? AFAIK this is just a configuration in ext_tables.php/TCA overrides?

Using the PageDoktypeRegistry class in the ext_tables.php of an extension :

$dokTypeRegistry = GeneralUtility::makeInstance(PageDoktypeRegistry::class);
$dokTypeRegistry->add($doktype,
  [
   'type' => 'web',
   'allowedTables' => '*',
  ]
);

I tried to reproduce it with the demo site https://demo.typo3.org/typo3 but I failed...
(Firefox 124.0.1 (64 bit) on MAC)