Anytime Google wanted to they could remove your ability to install Firefox or change duckduckgo. Microsoft is going to allow you to install another browser and change the search function in that browser but will not allow you to change Edge from its default status, meaning everything auto opens in Edge, not Firefox and Bing is the system wide search provider much like the Google bar at the top of Android and outside of your non-default installed browser you will have to use Bing.
I use standard unrooted android with firefox and duckduckgo. Most URLs open in firefox for me.
Anytime Google wanted to they could remove your ability to install Firefox or change duckduckgo. Microsoft is going to allow you to install another browser and change the search function in that browser but will not allow you to change Edge from its default status, meaning everything auto opens in Edge, not Firefox and Bing is the system wide search provider much like the Google bar at the top of Android and outside of your non-default installed browser you will have to use Bing.