Description
This implementation is using EIP-1538 for its upgrades. Specifically EIP-1538 is implemented in the contracts in the ProxyReceiver folder.
EIP-1538 has been abandoned and replaced by EIP-2535, the Diamond Standard.
EIP-2535, or the Diamond Standard, is an improvement over EIP-1538.
I suggest replacing the implementation of EIP-1538 in this repository with an implementation of EIP-2535. I suggest using the reference implementation of EIP-2535 to do this.
Some information about the Diamond Standard:
Here's a couple articles about EIP-2535:
Understanding Diamonds on Ethereum
Ethereum's Maximum Contract Size Limit is Solved with the Diamond Standard
One of the authors (Ronan Sandford) of ERC-1155 is currently building tooling for EIP-2535. Here is a link to his announcement: https://twitter.com/wighawag/status/1280992800545349644
I am the author of the Diamond Standard so if you have any questions or need help then let me know.