The Wayback Machine - https://webcf.waybackmachine.org/web/20210824160827/https://docs.github.com/en/communities/maintaining-your-safety-on-github/viewing-users-who-are-blocked-from-your-organization

Viewing users who are blocked from your organization

You can view a list of all users whom you or other owners have blocked from your organization. If a user was blocked for a specific amount of time, you can see the amount of time they were blocked for.

In the top right corner of GitHub, click your profile photo, then click Your organizations.
Next to the organization, click Settings.
In your organization's Settings sidebar, click Blocked users.
Under "Blocked users", review the list of users who are blocked from your organization.