TL;DR: If the user with the username you want is inactive, report it to Github on his profile. It's part of their name squatting policy, and you'll probably receive feedback.
It's been a long time since I've wanted to change my Github username, and I had the perfect candidate: 5 letters, exactly my nickname, and easy to say it (well, at least in portuguese...). But, unfortunately, it was already taken.
After reading about Github policies, I found this one telling that my long-desired username might be possible to get, since the user that had it previously was not active and his displayed e-mail address didn't exist (as I tried to contact him).
So, with a bit of hope, I've reported him explaining that the user was not active (didn't have any repositories nor activity in the last 5 years). One day later, I received this:
Instantly I've made the switch! I was already aware of the downsides (gists and mentions to you are not updated), but I've decided that it was worth it.

Oldest comments (31)
don't forget to update your profile with the new github account
Yeah, I will probably have to login again, because Dev.To failed to update it (it's not an input field).
Thanks for the heads up ;)
Congrats! I wanted a username too, I found it to be inactive, but it contain a repo. So they didn't released it for me
Try again later!
I think mine used to have a forked repo years ago...
How long did it take the support team to get back to you?
Only one day, Emma!
They just replied for me - looks like emma isn't available :(
Yeah, sorry about that. Seems @emma is an organization, so their policy might differ...
I think it had some private activity, so that's why :)
Congrats and thank you for the awesome idea. I've tried it and got my dream nickname. It was one week talking to support and to the old owner but apparently he had more than one account so he agreed to transfer it to me. :)
Nice I got one too! github.com/yg
It's dead. 404
Nice
Just login to say thank you! I also got the account name that I wished for a long time after sending a Name Squatting Notice to GitHub according your advice.
It also works for GitLab.com, though the wait time is a bit longer.
Sounds great.
Would anybody who was successful be able to share what they initially emailed? I'd like to give it a go and get the wording right to give me the best possible chance.
Where exactly can I report this ? Can someone help me?
Visit: support.github.com and create a new ticket.
The wait time has been increase drastically. You might have to wait 2-4 weeks for a initial response.
Btw, as of now Github is prohibiting users to claim taken usernames
docs.github.com/en/github/site-pol...
good luck
But here Name Squatting Policy shows you can report inactive user which is considered as future use.
It says it's prohibited
GitHub prohibits account name squatting (Not Reporting them), and account names may not be reserved or inactively held for future use. Accounts violating this name squatting policy may be removed or renamed without notice. Attempts to sell, buy, or solicit other forms of payment in exchange for account names are prohibited and may result in permanent account suspension.
Which option do I report it for?