Hello!
@heckflosse Ingo, good find! Yeah, that’s me. 
I have been using a setup like this @ggbutcher for my multi-dayhikes in the Alps for the last year now (offline and off-grid mostly), with RT 5.0 though which never really seemed to work on the Pi in a reliable way for me (mostly crashing when trying to save conversions of larger DNGs) - RT 5.6 works MUCH better, now that I got it to install! (thanks again to the great community here). With 5.0 it was more about the storage aspect in the end.
Glenn, I wish I had your expertise to try and pull off something similar! 
Trying to get RT 5.6 onto my Pi pushed me beyond my personal limits allready though.
I had the set with me in Venice over the last days (without the Solar panel) and I find it to be a very useable (albeit slow on the processing end) travel solution too. Being a SigmaProPhoto “victim” ever since the SD10 came out helped develop a certain mindset when it comes to slooooow RAW conversion though.
Best,
Alex