See for example here or find some more posts on this through the forum search. Basically, since FP2 runs with a Qualcomm Chipset, there are proprietary drivers involved. Those can only be provided by Fairphone as binary blobs (download them here) and not as human-readable code.
The license that comes with the binary blobs (find it here, too) sounds pretty restrictive, so that’s why @Max_S pointed out that the binary blobs aren’t even included in the build.