This has been brought up in the past so I apologize for requesting this myself, but it seems to have been a while since this request was made and perhaps people aren't aware.
Ecosia is a wonderful search engine that doesn't exploit your information like Google does, and uses its ad revenues to plant trees and fund environmental restoration projects in parts of the world that greatly need it. Even better, they are fully transparent about the money they bring in, how much is spent on salaries and upkeep, and how much gets donated to charities and foundations to further their cause. They post a financial report monthly on their site detailing all this.
Now, if there is a good reason on Opera's end not to add Ecosia as a selectable default search engine, then it would be amazing if we could create our own engines (which we can) and set them as default (which we can't).
Thanks so much for building an amazing browser and I hope you will consider this request for real this time around!