Regarding the Apeiron Protocol, with different collaborators I've developed several PoCs that demonstrate the core functionalities. These include:

Sign Project at DEVCON 2022: An initial proof of concept demonstrating the protocol's ability to create and manage Signs: https://ethglobal.com/showcase/sign-eip-1492-e89jh

ARCOiris Project at ETH Denver 2023: A follow-up PoC that showcased the protocol's capabilities in a more complex environment: https://app.buidlbox.io/projects/arcoiris

Github Repository: The Apeiron Protocol's EIP draft and other related work are publicly available on Github for review and contribution by the community:  https://github.com/eth-sign/apeiron-protocol/blob/main/apeiron-protocol.md