mixer.com keeps opening up in Edge on my Windows 10 laptop.

Lame! Try this maybe...

1. give "Settings" at the start bar
2. click "Apps" at the "Windows Settings" pane that appears
3. at "Apps & features" search for "Edge"
4. click on "Microsoft Edge" when it appears and then click the "Advanced options" link that is exposed by as much
5. click the "Reset" button here

 
 

Addendum 1/17/2019: This does not work. I am not sure what the fix is to get rid of mixer.com. mixer.com is of Microsoft and is not adware. It just looks like adware when it shows up in Edge. Microsoft is doing this to you.