The way he comes up with ideas is by living on the edge — as he puts it. He looks at new tech coming out by attending events and expos like GoogleIO where they introduce new tech.
He then tries to implement the tech/project with a problem he noticed earlier. Really simple and smart!
Going back to me, the way I come up with ideas is just by living life. I note down any problems or short ideas I get in my notion workspace. When I want to work on anything or if the problem is bugging me a lot I just build out a small MVP to test it out as I consider myself as an early customer.
There is an amazing article by PG about ideas — read it here.