There are two UIs Introduction - Turris Documentation
Turris team has decided to develop its own web administration interface due to complexity of the existing LuCI interface for basic users. Thus, came into being Foris, which is a simplified interface for administration requirements of Turris routers. It has been created in order to provide users with a simple and extensible administration and network configuration tool.
In short, re/Foris does not cover advanced settings.
Potentially good practise is getting acquainted first with the available documentation