Just saw on amazon a product with vegetable tanned leather. Is vegetable tanned leather plant-based or animal-based? If it is animal-based, so that I will not buy it, because I am against animal slaughter.
As @jsotola said in the comments, "vegetable tanned leather" means animal hide tanned with plant substances rather than with, for instance, chromium sulphate. "Vegetable-tanned leather", in other words, rather than "tanned vegetable leather"
There are, in fact, some very successful vegan leather substitutes available now, some made from plant materials and some from plastics. Leather substitutes seem to have come on a lot in the last few years. There are still some on sale that are really not much good, but, for instance, I have a very good pair of ankle boots from Will's Vegan Shoes that really are indistinguishable from leather (in breathability as well as looks) and were still going after a couple of years' hard wear. From the rather unclear explanation given on their website, I think those are an example of a plant-based one rather than a petrochemical one:
Created with Italian vegan leather made with plants using bio oil sourced from organic cereal crops grown in Northern Europe in a carbon neutral process.
As far as I know, however, none of these require any process that could be described as "tanning", so, if you see the word "tanning" on a leather product, like the backpack you asked about, that in itself indicates that it's ordinary animal leather.