Unfortunately, your options are limited here, but here's what you can try:
Contact GitHub Support at support.github.com — explain the situation. They may be able to verify your identity and help you regain access or delete the account.
Username squatting policy — GitHub has a policy where inactive/empty accounts can have their usernames released. Since your old account is empty, you can request this through support.
What to include in your support request:
The old username
Proof that it was your account (old emails, billing info, etc.)
Your current GitHub account
Request either account deletion or username release

Hi,

If you've lost access to both the email address associated with the account and the credentials required to complete 2FA, your options are unfortunately limited.

A few things you can try:

1. If you still have recovery codes saved from when 2FA was enabled, use those to regain access.
2. If you still have an active session on any device where you're logged in, try updating the email address and account recovery settings from that session.
3. If the email belonged to a former employer, you could check whether they can temporarily restore access to that mailbox, although many organizations will not do this for security reasons.
4. Contact GitHub Support and explain the situation. They can advise whether any account recovery options are available for your specific case.

Regarding the username, GitHub Community members cannot free, transfer, or reassign usernames. If the account remains inaccessible, GitHub Support would be the only team that can determine whether any action is possible.

Since you mentioned the account is essentially empty and your primary goal is to reuse the username, I'd recommend opening a support request focused on account recovery and username availability. Be prepared to provide any information that helps establish ownership of the original account.

A GitHub staff member may be able to provide more specific guidance, but in general, recovery depends on what account ownership information and recovery methods are still available.