To support environments like Microsoft GCC High, Quicklaunch can use alternative Microsoft Graph endpoints. 

The default endpoints for non-GCC are:

Login Url - 

Graph Endpoint -

If your organization is using a custom Login URL and Graph Endpoint URL (e.g. for GCC) it can be added under the Account Login Settings tab. See the picture below.

For US Government GCC environment, the alternate endpoints are:

Alternate Login Url -

Alternate Graph Endpoint -  

For other GCC environments see the following: