Another way 
First removing a background. I use a quick-n-dirty plugin isolate.py (attached, unzip, put in your plug-ins folder). Try it out on some representative images, if it works, great, if not then back to the drawing board.
The usual Gimp batch plugin BIMP is no good for these operations, fortunately there is a new one here:
https://www.gimpscripts.net/2021/09/gimp-batch.html
There are examples on that page and links to further discussions, do follow them up.
However, all being well, it might go like this 4 minutes duration: https://youtu.be/JNKpDGFVnm8
This the command used in the batch plugin
First removing a background. I use a quick-n-dirty plugin isolate.py (attached, unzip, put in your plug-ins folder). Try it out on some representative images, if it works, great, if not then back to the drawing board.
The usual Gimp batch plugin BIMP is no good for these operations, fortunately there is a new one here:
https://www.gimpscripts.net/2021/09/gimp-batch.html
There are examples on that page and links to further discussions, do follow them up.
However, all being well, it might go like this 4 minutes duration: https://youtu.be/JNKpDGFVnm8
This the command used in the batch plugin
Code:
pdb.python_fu_isolate(image,layer)