End-to-end process of building, validating, and distributing custom apps and add-ins across Microsoft 365 platforms
They can use the MyGroups portal: https://account.activedirectory.windowsazure.com/r#/groups
Therein, any user can see a list of groups they're a member of, as well as groups they own. Pressing the Join group button allows them to browse a list of groups within the tenant and request to be added.