I'm skeptical that this will give them enough control to fully customize all browser behavior. The platform-provided browser engine APIs (WebKit, the new WebView2 on Windows) are designed for simple HTML embedding scenarios, not a full web browser. I struggled with this when developing a browser based on the IE engine several years ago. I think Electron would be a better bet. Does anyone disagree
Imho they don’t aim to customize the UX that much. They’ll build something like their mobile browser and push for their search engine, mail protection and whatever they’ll try to sell in the future. And we should just not trust them. So many people use browsers as they are (which I find impossible nowadays with all the ads and popups) and reading that DuckDuckGo magically protected them will be enough for them.
Instead of Electron they could have just used Chromium but that is ethically terrible and an un useful effort for them (given what I said about their intentions).