BIMP is a graphical batch plugin to apply a set of GIMP manipulations on groups of images. You can use predefined manipulations like resize, crop, flip, rotate, color correction, sharpen, watermark, format conversion, rename, but you can also select other installed plugins or script-fu and apply them to each image.
How to convert color negatives with GIMP
Adjusting 35mm Film Negatives
How to Make GIMP Into a Negative
Negative Scanning Tip: Fix Grain and Noise Using GIMP
Using A USB Scanner With GIMP