TYPO3 Core

From the EN the requirement is:

User preferences
Where software is not designed to be isolated from its platform, and provides a user interface, that user interface shall
follow the values of the user preferences for platform settings for: units of measurement, colour, contrast, font type, font
size, and focus cursor except where they are overridden by the user.
...
For web content, the underlying platform is the user agent.

This epic is used to track the corresponding tickets for the various Problems that fall under this category. This includes, but is not limited to, respecting a user defined font size and the required adjustments of the user interface.