Token URI

To make this a complete example, the last thing that's missing is the TokenURI.

To make it work, our Smart Contract needs to implement the baseURI function:

//SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/Counters.sol";
import "./@rarible/royalties/contracts/impl/RoyaltiesV2Impl.sol";
import "./@rarible/royalties/contracts/LibPart.sol";
import "./@rarible/royalties/contracts/LibRoyaltiesV2.sol";

contract MinimalERC721 is ERC721, Ownable, RoyaltiesV2Impl {
    using Counters for Counters.Counter;
    Counters.Counter private _tokenIdTracker;

    bytes4 private constant _INTERFACE_ID_ERC2981 = 0x2a55205a;
    constructor() ERC721("Minimal", "MIN") {}

    function mint(address _to) public onlyOwner {
        super._mint(_to, _tokenIdTracker.current());
        _tokenIdTracker.increment();        
    }

    function setRoyalties(uint _tokenId, address payable _royaltiesReceipientAddress, uint96 _percentageBasisPoints) public onlyOwner {
        LibPart.Part[] memory _royalties = new LibPart.Part[](1);
        _royalties[0].value = _percentageBasisPoints;
        _royalties[0].account = _royaltiesReceipientAddress;
        _saveRoyalties(_tokenId, _royalties);
    }

    function royaltyInfo(uint256 _tokenId, uint256 _salePrice) external view returns (address receiver, uint256 royaltyAmount) {
        LibPart.Part[] memory _royalties = royalties[_tokenId];
        if(_royalties.length > 0) {
            return (_royalties[0].account, (_salePrice * _royalties[0].value)/10000);
        }
        return (address(0), 0);

    }

    function supportsInterface(bytes4 interfaceId) public view virtual override(ERC721) returns (bool) {
        if(interfaceId == LibRoyaltiesV2._INTERFACE_ID_ROYALTIES) {
            return true;
        }
        if(interfaceId == _INTERFACE_ID_ERC2981) {
            return true;
        }
        return super.supportsInterface(interfaceId);
    } 

     function _baseURI() internal view virtual override returns (string memory) {
        return "https://mydomain/metadata/";
    }

}

If you test it in the developer console, it will output you a url to a metadata file. Adjust it to your own server!