Solidity ERC721 – How to Distribute Royalties to Addresses with an ERC721

Opensea did not supports the BSC network. But you can mint the NFTs on Polygon for cheaper fees. Polygon is supported by Opensea platform.

Reference: Which blockchains does OpenSea support?

something like this is a bit expensive to set up, but minting is cheap, so I think it's along the lines of what you want to do.

Rather than keeping track of what's been minted already, it keeps a set of IDs that haven't been minted and selects from that. The set gets smaller as NFTs are minted.

    pragma solidity ^0.8.7

    import "hardhat/console.sol";

    contract RandomMints {

    uint[] notMinted;

    function createSet() external {
        // this is a bit expensive but a one off
        // txn gas 2282618 in remix
        for(uint i; i < 100; ++i){
            notMinted.push(i);
        }
    }

    function pickId() external returns (uint) {
        // txn gas 37430 in remix
        uint numLeft = notMinted.length;
        console.log("num of NFTs not minted:", numLeft);

        // pick a number between 0 - num of unminted NFTs -1
        uint rand = block.timestamp % (numLeft - 1);  //not really random
        uint idSelected = notMinted[rand];

        // now reduce the set. it doesn't matter if we mix up the order as it adds more entropy
        // get rid of the picked id by overwriting it with the last id/element
        notMinted[rand] = notMinted[numLeft -1];
        // pop the last (now duplicated) id/element off the array
        notMinted.pop();

        console.log("id selected:", idSelected);
        return idSelected;
    }
}