How to find your ERC165 interface bytes4 using Remix IDE

Helper.sol

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.20;

import "@openzeppelin/contracts/utils/introspection/IERC165.sol";

// @dev: replace this interface with your ERC165 interface
interface SomeInterface is IERC165 {
  function someFunction(uint256 id) external view returns (string memory);
}

// @dev: put this whole file in Remix and compile it.
//       after, deploy this Helper contract to any network.
//       lastly, call getInterface() to get your bytes4 value.
contract Helper {
  function getInterface() public view virtual returns (bytes4) {
    // @WARN: update this to refer to YOUR interface
    return type(SomeInterface).interfaceId;
  }
}

Since this is a predictable static call, you can use any network including the simulated shanghai network bundled with Remix to save time and money.