Mycroft GUI consist of two parts one an application that houses the mycroft skillview and second the library which provides the skillview. Both are part of the mycroft-gui repository.
The mark-2 prototype runs plasma-nano with the above mycroft-gui-mark-2 shell package that embeds the skillview directly into the shell so it runs as part of the shell and not inside the mycroft-gui application.
To better explain the “mycroft-gui-mark-2” package is a shell package for plasma nano that embeds the mycroft skillview onto the shell itself and also provides configuration to set the orientation, it provides support for a virtual keyboard, and provides some basic GUI interface for settings like wifi. All of this is provided in this package as plasma-nano is a much reduced package with lesser dependencies compared to what plasmashell provides on the desktop, The orientation is basically of the skillview and the shell, it shouldn’t be needed on a normal screen unless someone wants to build some custom enclosure with a rotated screen.
There really isn’t a direct concept of landscape/portrait mode since the skillview simply can utilize the whole screen if embed in a shell or whatever window like the GUI application, the skills should simply adjust to the screen/resolution, (it largely depends on skill devs to create response designs with qml, all of the current skills that implement a GUI are responsive so they should have no issues being displayed in any form factor / orientation )
Plasma Bigscreen is also based on plasma-nano but we use the mycroft-gui application to display the voice apps/skills in a window rather than embedding the skillview into the shell itself as bigscreen has a larger usecase of being able to use multiple applications.