Great article! Very thorough. Just a heads up, if you want to reduce the risk of working with wallet private keys or mnemonic phrases, check out the Truffle Dashboard.

It's compatible with Hardhat (I'm actually just about done an article on this) and makes deploying to different networks super easy. It routes all transactions through your browser wallet without needing to expose the private key. You can deploy to any network you can connect your wallet to, while only needing to set up the dashboard in your config file