I tried to see what could be done in your case. Often these emails also include a direct link to revert the change if it wasn't authorized by you. From the ss, it looks like it is missing, but check again. If it is still missing, use the link for contacting GitHub. Give them your original username, the original email address, and explain exactly what happened. Once you have done that, start prepping your proof of ownership like SSH Private Keys, PATs or OAuth tokens, billing info, commit history & git config. Hope this helps.