You can try talking to Gitlab support. I've found Github to release squatted usernames, so that might be the case with Gitlab too. Remember, however, all that

You can try talking to Gitlab support. I've found Github to release squatted usernames, so that might be the case with Gitlab too. Remember, however, all that their activity need not public. They could have a massive organisation with tons of active private repos. Still, doesn't hurt to ask.