Isn’t it obvious? My G'MIC fun with afre thread almost exclusively deals with gradient_norm. So, any issues I have had with it are thorns in the flesh. Not necessarily improve but questing to find a better solution; my princess might be in another castle.
I was debating whether to put this in the processing category or gmic. I use gmic so gmic it was. But definitely applicable elsewhere like GIMP and Krita.