What chain is Altura on?

As a cryptocurrency enthusiast and investor, I'm curious about the technical underpinnings of various blockchain projects. One such project that has piqued my interest is Altura. Could you please elaborate on the blockchain infrastructure that Altura utilizes? I'm specifically interested in knowing if Altura is built on an existing, well-established chain such as Ethereum or if it has opted for a custom-built solution. Understanding the underlying technology is crucial in evaluating the project's potential and long-term sustainability.