Wow, what a tremendous piece of art!
Everything ran w/o any problems. Only thing were the warnings installing the mrpi packages "mounting ro failed" or similar. But beside those everything works so far: the librariansync, the USBNetwork and of course the ScreenSaver.
Simply perfect and so Amazon was in a position again to sell me new stuff, this time a Kindle PW4 which I'd never bought knowing there is no jailbreak for it.