In addition to seeing the services you own in the My Services tab, you can add services by subscribing to their groups. You will not be marked as an owner of the services in the groups, but it will appear in your “My Services” tab.
You can set permissions for group subscriptions at:
Example: An SRE who does not officially own a service but who wants to see related notifications can “subscribe” to a group. This user will not appear as an owner on the Service Details page, but the services will appear in their My Services tab, making it easy for team members to check in on relevant entities.