As I have been reading, I believe it has been Pliny making the case that the pre-Law world, and not just Abraham and Jacob, practiced tithing as an act of religious devotion.
IF this is true (as I haven't searched it out for myself) then I would offer this counter-argument:
In
1 Corinthians 10:20, Paul makes it clear that whatever Gentiles sacrifice, they sacrifice to devils, and not to God. Tithing as an act of religious devotion, is a sacrifice.
If any pre-Law Gentiles offered a sacrificial tithe to their god or gods, then such a tithe went to a devil or devils.
Paul wrote that he doesn't want us to have any fellowship with devils.
If the doctrine of tithing for New Covenant saints is to be proven using the above line of reasoning, i.e. that pre-Law heathens tithed to their gods, then, the alleged New Testament doctrine of tithing is being associated with demonic sacrifices.
Not a route anyone should ever want to go.