I gladly found out that I can run NoMachine on my old tablet stuck with Android 4.4.
At least I can now take my linux desktop into my sleeping room …
But what I cannot figure out and no searches helped me:
I understood I should simulate a right mouse click by tapping on the screen and hold the finger on it (=the screen).
But as soon as I leave my finger on the screen for just a glimpse of a moment longer, the setting menu will appear as a screen overlay. To make things worse, the mouse will be in the right bottom corner after I leave the settings screen.
I think I don’t see the obvious?