Users have the ability to restrict access to Projects to specific users from the iOS app.
Note: This feature is for users on a “Team” plan or higher.
Setting the project access
Owners, Admins and Full Access members on a workspace can set a project to be either Internal or Invite-Only during project creation, and after from Project Settings.
Internal: The Project is accessible by anyone who has access to the Workspace or who’s directly invited to the Project.
Invite-Only: Restricts access to the project to only those directly invited to the Project. Note that admins still have access.