Certainly, the 'convert to cube' option is no longer displayed in the object menu or context menu... All features related to modern primitives are located in the N-Panel. For the time being, you will need to manually register the shortcut keys from there (if you need).

UV mapping options are located in the UV panel at the bottom of the Geometry Modifier for ModernPrimitive. Currently, users cannot freely perform UV unwrapping. Since UV coordinates are stored as attributes rather than vertex information of the model, please use the Attribute node in the shader to retrieve and use the coordinates.