Based on this part of the My Team documentation: https://docs.microsoft.com/en-us/viva/insights/use/myteam#group-insights and the requirements in the Group Insights documentation you linked, Group Insights is only available to qualified managers. Part of the qualification is that their reports must be licensed for WPA/Viva and they also must be set up as a Manager within WPA/Viva.
So to answer your question, it is not enabled by default you must go through the onboarding process and set up WPA and enable Manager Settings for the Managers you want Group Insights for.
