I'm curious if you know of any reason to buy Shift besides specifically supporting German economy instead of the Dutch one

And would you know why they don't work together? At least on the software side that's easy to do remotely. I know Fairphone has been struggling to catch up with the machine learning and other services other vendors are adding on top of e.g. the camera sensor to get good photos. They seem to be doing better now but Shift seems to still have a lot of software bugs, eyeing their forums

I'm a bit worried by their lack of focus, though - looks like they are spreading themselves a bit thin, they are trying to build a lot of different gadgets all at once (keyboards, speakers, laptops, headphones, etc). Building a phone is hard enough, trying to build all other things might dilute the valuable development resources.