I didn’t find the peanut rubber, but did find that

Dr. George Washington Carver’s work resulted in the creation of more than 300 products from peanuts, contributing greatly to the economic improvement of the rural South. source

OP’s article states that

He helped Henry Ford make peanut rubber for cannons for World War II.

But I can’t find a actual source for that just endless repeated comments to that effect. I wonder if whoever-originated-that-idea conflated Carver’s peanut work with his other work with Ford:

By the time World War II began, Ford had made repeated journeys to Tuskegee to convince Carver to come to Dearborn and help him develop a synthetic rubber to help compensate for wartime rubber shortages. Carver arrived on July 19, 1942, and set up a laboratory in an old water works building in Dearborn. He and Ford experimented with different crops, including sweet potatoes and dandelions, eventually devising a way to make the rubber substitute from goldenrod, a plant weed. Carver died in January 1943, Ford in April 1947, but the relationship between their two institutions continued to flourish. Source

Idk about peanut rubber but I remember learning about dandelion rubber that was used for tank treads among other things. Guess there’s a lot of plants that can get turned into rubber if you’re desperate enough!

It had the properties of both peanut and rubber.