documentation, The first sprint release of the upcoming #TYPO3 version 13 offers a nice feature:
configurable backend URL,
thanks to @bnf who implemented it.
TYPO3 Explained now offers a chapter describing what you need to know about it and how to configure it: https://docs.typo3.org/m/typo3/reference-coreapi/main/en-us/Configuration/BackendEntryPoint/Index.html