So I have the following problem. I created an entry page with module front that has two links. To categoryA and categoryB. Now I want these two categories to have different front pages with different themes.
Any ideas on how I can achieve that?
Have you tried the ThemeKey module?
ThemeKey allows you to define simple or sophisticated theme-switching rules which allow automatic selection of a theme depending on current path, taxonomy terms, language, node-type, and many, many other properties. It can also be easily extended to support additional properties exposed by other modules.