[techas]

This kind of animal glues have some nice properties than “white glue” miss, e.g. you can remove it with heat. Traditional woodworkers still use it. You can buy it today: https://www.fine-tools.com/oberfl.html

[mauvehaus]

I use it for most glue-ups. I'm a big fan of Old Brown Glue:

https://oldbrownglue.com/

Great stuff, and the videos they put out are outstanding as well. The one about veneering a column is highly worth watching and illustrates the advantages of an animal protein glue in a real application.