Darktable generates .xmp sidecar files w/ the filename pattern FILE.CR2->FILE.CR2.xmp . Geeqie appears to not recognize this, and appears to accept only FILE.CR2->FILE.xmp . Adding CR2.xmp to the sidecar extension list does not appear to work.
Patch to allow suffix matching of extensions w/ '.' in them
The same problem exists with digikam. It also uses FILE.cr2.xmp naming scheme for sidecar files. As effect, Digikam doesn't see keywords assigned to photos in Geeqie. From what I see, it's probably incorrect behaviour (at least, Adobe uses the same naming as Geeqie).