There are several definitions, most exclude digital prints and some exclude silver-gelatin prints. Most agree that non-silver contact printing processes such as Platinotype, Palladiotype, Cuprotype, Cyanotype, Gum Bichromate, and Carbon are Alt-Photo. And most agree that silver image prints such as Vandyke Brown, Argyrotype, Salt Prints, and Albumen Prints are Alt-Photo.
Many practitioners use digital negatives to print the image, but some purists might exclude any process that uses digital technology. I use traditional large format cameras and digital cameras to get a negative to contact print the image.
Following are some of the alt-photo processes that I've created and others that I've experimented with. Hope you enjoy.