Just wanted to let you know that I wrote a tool to automatically georeference and crop topo maps at https://github.com/ramSeraph/topo_map_processor

It is a bit clunky to use where you have to fiddle with the various parameters but it has got the job done before. It uses image processing to locate the corners of the map and along with an index file containing sheet number to the corner coordinates, georefences and crops the toposheet and emits a Cloud Optimised Geotiff.

This has been used to automatically georeference and clip Survey Of India’s and some other topo map series from the subcontinent.

Hope that helps.