Thanks for the report, we’re tracking this bug here:
To help with your issue right now though, we can do two things:
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You can use passwordless, google or firefox accounts to log into the original email on your original account (which is now possible)
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Merge your accounts and update the address on your original account to the new GitHub email - you’ll still be able to log in with passwordless, google or firefox accounts if any of them are set up with that new email.