TYPO3 v8 has reached its end-of-life March 31st, 2020 and is not maintained by the community anymore.
You can order Extended Long Term Support (ELTS) here: TYPO3 ELTS.
User Settings Configuration¶
The User Settings module has the most complex form in the TYPO3 backend not driven by TCA/TCEforms. Instead it uses its own configuration array. It is quite similar to the $TCA, but with less options.