Working on a new tablet with Windows 10 installed, I recently discovered that I could not set the default web browser to Firefox – my browser of choice. No matter what I did it seemed to only accept Microsoft Edge. In fact when I went to Settings, System, Default Apps all I saw was a plus icon and the choose a default prompt. Tapping the icon gave me a choice of browsers but selecting anything other than Edge failed.
So I decided to stay old school and went via Control Panel. In the Category View you can tap on Programs and then tap on Default Programs. In the Small or Large Icons view, tap the Default Icons option. Either way you finally tap on the Set your default programs option that is eventually displayed. Tap the browser of your choice and tap on the Set this program as default option on the right. It worked for me!