X11 linux RaspPi Android

[Roger Morrell]

I have built 

a "standard" linux version of my Kivy app and it runs in X-windows

a Rasp Pi linux version and it  wont run it x_windows but runs on the full screen.

In reading through the postings other people have noticed this and it appears to be deliberate, although others  note it as a discovery by experiment rather than something that is deliberate.  - this this documented anywhere ?  and the posting were were several yeras old and I wondered if the official position had changed.

Seeing my Pi version is run on a small screen this is good.  But it appears to be confused which screen to run in when I have the small LCD screen (target screen) and an HDMI monitor. Is there a way on the RaspPi of controlling which screen?

Finally I'm also trying to build and Android version and when running buildozer one of the many failures I encountered was when it was trying to include the python3 X11 modules.  It seems that it should never to do this for Android.  Is there a way of specifying up front that X11 is not needed ? I had thought it might be around the use of SDL2 - except that it is used in both the standard x-ll linux version and the full screen Rasp Pi version?

Roger