https://play.google.com/store/apps/details?id=com.app.rapusia
This browser is based on the chromium open source.
The customer can build the chromium source using ninja and gn configuration for each platform: android, ios, iMac, windows and linux.
But there is not some limit to customize the chromium as you want.
For the android platform, I have converted the chromium ninja project into android gradle project.
So it is easy to customize the chromium for the native android developers who is experienced with java.
This browser has only dedicated search engine. Only one search engine is possibile in this app. The config of it is writen in the chormium engine source with c++.