The claim that there is no single universally accepted true set theory is common knowledge within mathematical logic and foundational set theory, where alternative systems like ZFC, constructive set theories, and various extensions coexist without a single canonical choice.
The claim is a well-established foundational fact in mathematical logic and set theory. Different axiomatic frameworks (such as Zermelo-Fraenkel set theory with or without choice, constructive set theories, and alternative foundations) exist, and there is no single universally accepted foundational axiom system for all of mathematics, making it common knowledge in the context of logic and set theory.