Thanks for your further replys.
I was using PPG, the default of darktable. Changing it to AMaZE seemed to not make much difference, changing it to VNG4 decrease the contrast of the grey stripes a little – but they’re still dominant visible, and the yellow and green ones obviously even more.
I did understand that it might be helpful to decrease the difference between the two ISO values (meaning to decrease the +3EV) and additionally to maybe choose a different pair of ISO values all together (if the scene/exposure time) permits. For the used Canon EOS 5d Mark III one reasonable ISO value seems to be ISO 3200 (maybe ISO 6400 using the zoom lens with extender).[1] I’m not totally sure (especially after reading You probably don’t know what ISO means – and that’s a problem) if my other ISO value should be lower or higher though.
I’ll anyway need to wait a couple of years to try different settings as recommended for the next lunar eclipse photos. 
But I’ll continue to experiment and come back if I have additional questions.
Thanks again!
Simon
[1] https://www.lonelyspeck.com/milky-way-exposure-calculator/