I’d note that these two problems are of different severity. The fisheye effect on the wide angle camera is likely just the unadjusted output from the camera, and can be adjusted later. For example, I posted a lensfun file here with some rough parameters for adjustment. It’s possible that this could be handled by third-party camera apps without any changes by Fairphone.
The 48MP problem, on the other hand, can’t be worked around, though it’s hard enough to use reliably on the stock OS to begin with.