Can I Run This on a Folder That Is Not From Google?
Yes. Any folder of photos works. Here is what it can do with files that never touched Google Photos.
Yes. The Google Takeout case is what it was built for, but nothing about it requires Google.
Point it at a folder from an old hard drive, a camera card, a phone backup, or a shared drive full of family pictures. It reads whatever each file already knows about itself, corrects the file dates to match the real capture date, and sorts everything into the structure you choose.
That covers the common mess: a decade of photos in one folder with names like IMG_4471.jpg, or a drive where every file says it was created the day you copied it.
You get the same result either way. Files named by date and place, folders by year and month, HEIC converted if you want it, screenshots moved aside, and duplicates skipped when you merge into a library you already have. The first 500 photos are free, so try it on one folder before the whole drive.