2 is what I’ve installed in the houses I’ve renovated. It’s just not worth the risk to your electronics and home itself to cheap out on proper electrical in your house. Particularly if you’re one of those people with a 12 core 20tb dell r720 in the basement.
Our house was built in the 70's and that is what we used to have. After we upgraded our panel though we got not 1, but 2 grounding rods.