Welcome to the community!
Not really! I suspect your GitHub and GitLab accounts use the same email address. On SonarCloud, the email address must be unique across all users. To make it possible to login with multiple ALM accounts that share the same email address, what we do is show a warning like this:
The only thing that’s deleted is the email field of the previous account (in your case GitHub), so that the address can be used in the current one (in your case GitLab).
If your account on GitHub still exists, you can log back in with it. When you do, you will get the same warning again, de-associating your email address from your GitLab account, so that it can be used with the GitHub account. As an admin of the org, you can grant admin permission to your GitLab account, and continue to use it.
Note that organizations are linked to accounts. So you cannot transfer the organization itself to your GitLab account. Currently the only way to do that is to delete the organization linked to GitHub, and recreate a new one linked to GitLab.