“Tallow” is juat a fancy word for “beef fat” (like pork fat/bacon grease/lard, etc.).
https://www.amazon.com/Beef-Tallow/s?k=Beef+Tallow
McDonald’s used to use beef tallow for fries in the 1960’s...but it is more expensive than “vegetable” (seed) oil...so they switched.
Other “vegetable oil” info:
Well whatever McDonalds uses now is nasty.
Is tallow the same as suet?
I used to be able to buy suet for pennies, to make bird cakes. This was back when supermarkets still did butchering in-house. Now, you have to go to a specialty butcher for it.
(I know the Brits have some processed and packaged types. It’s used commonly in Christmas Plum Puddings.)