Block/Censor NFT marketplaces that don't honour royalties - https://www.youtube.com/watch?v=pdvnUMz1U8o

AllowedMarketplacesNFT.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;

import "@openzeppelin/contracts@4.7.3/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts@4.7.3/access/Ownable.sol";
import "@openzeppelin/contracts@4.7.3/utils/Counters.sol";

contract MyToken is ERC721, Ownable {
    using Counters for Counters.Counter;

    Counters.Counter private _tokenIdCounter;

    mapping (address => bool) public allowedMarketplaces;

    constructor() ERC721("MyToken", "MTK") {}

    function safeMint(address to) public onlyOwner {
        uint256 tokenId = _tokenIdCounter.current();
        _tokenIdCounter.increment();
        _safeMint(to, tokenId);
    }

    function approve(address to, uint256 id) public virtual override {
        require(allowedMarketplaces[to], "Invalid marketplace, not allowed");
        super.approve(to, id);
    }

    function setApprovalForAll(address operator, bool approved) public virtual override {
        require(allowedMarketplaces[operator], "Invalid marketplace, not allowed");
        super.setApprovalForAll(operator, approved);
    }

    function setAllowedMarketplace(address marketplace, bool allowed) public onlyOwner {
        allowedMarketplaces[marketplace] = allowed;
    }
}

BlockedMarketplaceNFT.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;

import "@openzeppelin/contracts@4.7.3/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts@4.7.3/access/Ownable.sol";
import "@openzeppelin/contracts@4.7.3/utils/Counters.sol";

contract MyToken is ERC721, Ownable {
    using Counters for Counters.Counter;

    Counters.Counter private _tokenIdCounter;

    mapping (address => bool) public blockedMarketplaces;

    constructor() ERC721("MyToken", "MTK") {}

    function safeMint(address to) public onlyOwner {
        uint256 tokenId = _tokenIdCounter.current();
        _tokenIdCounter.increment();
        _safeMint(to, tokenId);
    }

    function approve(address to, uint256 id) public virtual override {
        require(!blockedMarketplaces[to], "Invalid marketplace, not allowed");
        super.approve(to, id);
    }

    function setApprovalForAll(address operator, bool approved) public virtual override {
        require(!blockedMarketplaces[operator], "Invalid marketplace, not allowed");
        super.setApprovalForAll(operator, approved);
    }

    function setBlockedMarketplace(address marketplace, bool blocked) public onlyOwner {
        blockedMarketplaces[marketplace] = blocked;
    }
}