About visibility changes for projects
You can restrict who has the ability to change the visibility of projects and classic projects in your organization, such as restricting members from changing projects and classic projects from private to public.
You can limit the ability to change project and classic project visibility to just organization owners, or you can allow anyone granted admin permissions to change the visibility.
This option may not be available to you if an enterprise owner restricts visibility changes for projects and classic projects at the enterprise level. For more information, see "Enforcing policies for projects in your enterprise."
Allowing members to change project visibilities
In the top right corner of GitHub.com, click your profile photo, then click Your organizations.
Next to the organization, click Settings.
In the "Code, planning, and automation" section of the sidebar, click Projects.
To allow members to adjust project visibility, select Allow members to change project visibilities for this organization.