Hello Paddy,
You can use the Set a default associations configuration file Group Policy or the DefaultAssociationsConfiguration Mobile Device Management setting to set Microsoft Edge as the default browser for your organization.
The default file associations aren't applied if Microsoft Edge isn't installed on the target device. In this scenario, users are prompted to select their default application when they open a link or a htm/html file.
For better understanding look at the the article below,
https://learn.microsoft.com/en-us/deployedge/edge-default-browser
Hope this answers all your queries, if not please do repost back.
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