Important: #100634 - Rich Text Editor always enabled per user¶
Back in TYPO3 v3.x there was an RTE integrated into TYPO3 which only worked
in Internet Explorer 4+, but not in Mozilla / Firefox browsers. This was a
huge mess, as not every user / client was able to use an RTE and instead to had
to write pure HTML in a
<textarea> input field with special tags ("typolink" etc).
Since TYPO3 v4 a huge effort were made to integrate HTMLarea as Rich Text Editor, which was forked and developed by the TYPO3 community. It was then possible for most users working with a real RTE.
In v8, TYPO3 migrated towards CKEditor 4 as a dependency, and CKEditor 5 with TYPO3 v12, the Rich Text Editor is working very browser-native for modern browsers without an iframe around the RTE.
A lot of legacy code was moved and migrated, however, one option - the option to deactivate the Rich Text Editor on a per-user basis - which was necessary in TYPO3 v3, has now been removed, as it is not needed in 99.99% of TYPO3 installations and users anymore nowadays.
The previous user TSconfig setting
setup.edit_RTE has no effect anymore.