Short answer
HubSpot's KB: the Google Chat app manages notifications, connects Google Chat to your inbox or help desk, and previews links for contacts, companies, deals, tickets, emails, blog posts, dashboards and reports. Setting it up for all users needs Super Admin or App Marketplace permission plus Google admin rights.
1. In HubSpot
The relevant screen in my demo portal.

2. Worth knowing
If setup loops, the KB suggests asking your Google admin.