Universal Containers (UC) has implemented a multi-org architecture in their company.

Activating My Domain allows each org to have a unique domain name that can be branded to the specific business use case2. This can help users identify which org they are logging into and avoid confusion. Implementing SP-Initiated Single Sign-on flows enables users to start from a service provider (such as Salesforce) and be redirected to an identity provider (such as Active Directory) for authentication3. This can also allow deep linking, which means users can access specific resources withinthe service provider after logging in4. These two recommendations can address the complaints of the users who have licenses across multiple orgs.