Has anyone discovered a rishon

Answer 1

Apparently not. The Wikipedia article on Rishons sums it up quite nicely: "Currently, there is no scientific evidence for the existence of substructure within quarks and leptons, but there is no profound reason why such a substructure may not be revealed at shorter distances." In summary, the rison model proposes that leptons (such as electrons) and quarks (which make up protons and neutrons) are made up of smaller particles; such particles have not been discovered yet; but they might still be discovered.

Answer 2

Yes, Avraham ibn Ezra was a prominent medieval Spanish Jewish poet, philosopher, and scholar considered a Rishon in Jewish tradition. He is recognized for his extensive commentaries on the Torah and other biblical texts, as well as his contributions to Hebrew grammar and Astrology.