I just did a little experiment, copied /usr/share/megapixels to ~/.config and toggled the setting again. No change either. The toggle state is persisted but that's all that happens. Responsible fpr writting the raw .dng file is postprocess.sh and that has not been modified by megapixels, whether it was in /usr/share or in ~/.config. I have no idea how this feature is even supposed to work.

I did pay with the postprocess.sh script and as far as I can tell that works. However, Megapixels seems to pass 1 as argument no matter what, hence the .dng files are not removed. I have yet too look at why that happens.

Issue now tracked here: https://gitlab.com/postmarketOS/megapixels/-/issues/22