What chain is XRD on?

Could you please elaborate on the underlying blockchain that XRD, or Radix Delegated Proof-of-Stake (RDPoS), is operating on? I'm interested in understanding the technological foundations of this cryptocurrency and its potential advantages over other blockchain platforms. Specifically, is XRD built on a proprietary blockchain, or is it leveraging an existing blockchain solution such as Ethereum, Solana, or another popular platform? The answer to this question will help me assess the scalability, security, and overall potential of the XRD ecosystem.