The following procedure works in Build 10565:

  1. Browse to the web site of your desired Search engine (Google, Duck Duck Go, etc)
  2. Click on the three dots in the upper right corner
  3. Click on Settings
  4. Scroll to the bottom and click on View Advanced Settings
  5. Scroll down to Search the Address bar with and click on change
  6. Under Search With, highlight your new search engine choice and click on Set as Default