The clearer the problem is presented the better. I have GIMP 2.10 and G’MIC 2.9.0.
Before (100% zoom)
After (100% zoom)
Remarks
Issues The filter doesn’t remove the patterning (in the preview and after applying). It not only alters the colour (after applying only), it also generates patches of discoloration (after applying only).
Experiment I wrote a simple filter to see if I could remove the pattern. Looks like the pattern is too indistinct to attenuate properly. The softness could be due to camera shake or image compression.