Note: PolicyPak Cloud already has the Office2016/Office365 ADMX settings available in the Cloud and they can be accessed via the PolicyPak Admin Templates Manager built-in cloud editor.‌

For the PolicyPak OnPrem version, you can download the Office 365 ADMX files from here - https://www.microsoft.com/en-US/download/details.aspx?id=49030 for use in your On-Prem environment.

Also, this policy will not work for Microsoft 365 Apps for Business, See Group Policy Support section in the table at the link below: 
https://learn.microsoft.com/en-us/office365/servicedescriptions/office-applications-service-description/office-applications-service-description

¹¹ Limited to policies for web apps and privacy policies for client apps.

SCENARIO 1: Using PolicyPak Cloud

Create a new Admin Template policy with the appropriate setting from the ADMX template (use Keyword section to search):

Now set the value to “System default browser” instead of “Microsoft Edge” in the policy:

SCENARIO 2: Using PolicyPak On-Prem

Once Office ADMX is deployed, create a new Admin Template policy with the appropriate setting from the ADMX template (use Keyword section to search):

Now set the value to “System default browser” instead of “Microsoft Edge” in the policy:

Verification:

BEFORE:

AFTER: