Microsoft really wants people to use Edge as their default browser. For now they've been content with reminding the user when they try to switch the default browser or when they open HTML files, but they've got a new strategy.
When you open the installer for Chrome or Firefox, Windows 10 will present a popup window suggesting you to use Edge instead:
This popup is currently only showing in Windows 10 Insider Build 1809 and only time will tell if it will get into the stable release.
UPDATE - 15 Sept
Microsoft has replied to the situation. They will remove the prompt from the stable release as this was a test for Insiders only.
We've tested this functionality with Insiders only - The Windows Insider Program enables Microsoft to test different features, functionality and garner feedback before rolling out broadly. Customers remain in control and can choose the browser of their choice
Source - Thanks, @SaberLilly!
Last edited by smileyhead,