How to fix "Unidentified contract"? OpenSea is unable to “understand” ERC1155 - ethereum

Question

I have deployed a ERC-1155 based contract (based on OpenZeppelin) and minted some NFTs on this contract successfully. But when I want to use these NFTs in OpenSea, it always says "Unidentified contract".
Example: https://testnets.opensea.io/assets/0xc7d3e4a5A0c3e14ba8C68ea1b8a99a9dBf3ca76F/2
API-Example: https://testnets-api.opensea.io/api/v1/asset/0xc7d3e4a5A0c3e14ba8C68ea1b8a99a9dBf3ca76F/2/?force_update=true
Following their official Tutorial repository (which does not compile any more because of outdated dependencies and other issues) I have added some (maybe) opensea-specific functions and data that might required for OpenSea in order to work properly. However, OpenSea is able to grab all required data to display an NFT, but as long as they say "Unidentified contract", this all makes no sense so far.
My question has:
has someone already managed to deploy a ERC-1155 and used it with OpenSea properly without this issue? Is there anything we have to "register" somehow contracts that are not based on ERC-721?
🔢 Code to reproduce
import "#openzeppelin/contracts/token/ERC1155/ERC1155.sol";
import "#openzeppelin/contracts/access/AccessControl.sol";
import "#openzeppelin/contracts/security/Pausable.sol";
import "#openzeppelin/contracts/token/ERC1155/extensions/ERC1155Burnable.sol";
import "#openzeppelin/contracts/utils/Counters.sol";
import "#openzeppelin/contracts/access/Ownable.sol";
contract OwnableDelegateProxy { }
contract ProxyRegistry {
mapping(address => OwnableDelegateProxy) public proxies;
}
contract MetaCoin is ERC1155, AccessControl, Pausable, ERC1155Burnable {
bytes32 public constant URI_SETTER_ROLE = keccak256("URI_SETTER_ROLE");
bytes32 public constant PAUSER_ROLE = keccak256("PAUSER_ROLE");
bytes32 public constant MINTER_ROLE = keccak256("MINTER_ROLE");
address proxyRegistryAddress;
constructor(address _proxyRegistryAddress) ERC1155("https://abcoathup.github.io/SampleERC1155/api/token/{id}.json") {
_setupRole(DEFAULT_ADMIN_ROLE, msg.sender);
_setupRole(URI_SETTER_ROLE, msg.sender);
_setupRole(PAUSER_ROLE, msg.sender);
_setupRole(MINTER_ROLE, msg.sender);
proxyRegistryAddress = _proxyRegistryAddress;
}
function setURI(string memory newuri) public onlyRole(URI_SETTER_ROLE) {
_setURI(newuri);
}
function pause() public onlyRole(PAUSER_ROLE) {
_pause();
}
function unpause() public onlyRole(PAUSER_ROLE) {
_unpause();
}
function supportsInterface(bytes4 interfaceId)
public
view
override(ERC1155, AccessControl)
returns (bool)
{
return super.supportsInterface(interfaceId);
}
function mint(address account, uint256 id, uint256 amount, bytes memory data)
public
onlyRole(MINTER_ROLE)
{
_mint(account, id, amount, data);
}
function mintBatch(address to, uint256[] memory ids, uint256[] memory amounts, bytes memory data)
public
onlyRole(MINTER_ROLE)
{
_mintBatch(to, ids, amounts, data);
}
function _beforeTokenTransfer(address operator, address from, address to, uint256[] memory ids, uint256[] memory amounts, bytes memory data)
internal
whenNotPaused
override
{
super._beforeTokenTransfer(operator, from, to, ids, amounts, data);
}
/**
* Override isApprovedForAll to whitelist user's OpenSea proxy accounts to enable gas-free listings.
*/
function isApprovedForAll(
address _owner,
address _operator
) public override view returns (bool isOperator) {
// Whitelist OpenSea proxy contract for easy trading.
ProxyRegistry proxyRegistry = ProxyRegistry(proxyRegistryAddress);
if (address(proxyRegistry.proxies(_owner)) == _operator) {
return true;
}
return ERC1155.isApprovedForAll(_owner, _operator);
}
}
💻 Environment
node: v16.7.0
deps:
"#openzeppelin/contracts": "^4.3.0",
"#nomiclabs/buidler": "^1.4.8",
"#nomiclabs/hardhat-ethers": "^2.0.2",
"#nomiclabs/hardhat-etherscan": "^2.1.1",
"#nomiclabs/hardhat-waffle": "^2.0.1",
"#openzeppelin/hardhat-upgrades": "^1.9.0",
"#typechain/ethers-v5": "^6.0.5",
"#typechain/hardhat": "^1.0.1",
"#types/chai": "^4.2.15",
"#types/chai-as-promised": "^7.1.3",
"#types/mocha": "^8.2.2",
"#types/node": "^14.14.37",
"chai": "^4.3.3",
"chai-as-promised": "^7.1.1",
"chai-datetime": "^1.8.0",
"ethereum-waffle": "^3.3.0",
"ethers": "^5.4.5",
"hardhat": "^2.6.1",
"hardhat-typechain": "^0.3.5",
"ts-generator": "^0.1.1",
"ts-node": "^9.1.1",
"typechain": "^4.0.3",
"typescript": "^4.2.4"

Answer 1

This is taken from name in your contract.
For ERC-1155 tokens, add a public variable name
string public name = "My Collection Name";

Answer 2

I finally found the root cause! OpenSea expects a public property called name in order to display the proper Name of the Collection instead of a static label Unidentified contract.
I came across this while looking at their reference code (which depends on a now 3-year-old MultiToken-Contract implementation and needs all in all some downgrades of Node and other tools in order to get it build [a downgrade to Node 10 worked best for me today] ).