Pretty sure you can change your GitHub username. At least I did, but it's been awhile. When I got serious about my career I changed my professional online presence to use my real name.
Iirc it said something like, urls using your old username continue to work until someone comes along and makes a new account using your abandoned name.
Edit: here's GitHub's current docs on this, there's a few gotchas worth considering... https://docs.github.com/en/account-and-profile/setting-up-and-managing-your-personal-account-on-github/managing-personal-account-settings/changing-your-github-username
Ah, crap. Guess you're going to have to change your actual name then!