Since the store link is dead, you must source archived files like the Opera Mini.appx or Opera Mini.xap from community repositories such as WindowsViet or other legacy app archives. :
: If your build of Windows 10 Mobile supports it, simply open the .appxbundle or .appx file directly on the phone. opera mini xap for windows 10 mobile work
may still have active download mirrors for version 9.1.0.232. Step 3: Install the File Opera Mini XAP for Windows 10 Mobile: Does It Still Work
Yes, you can still get to work on Windows 10 Mobile by sideloading the original .xap or .appx files. Since the app has been retired from the Microsoft Store, manual installation is the only remaining method. Where to Find the Files Microsoft Edge : The default browser on Windows
The core functionality of Opera Mini relies on a server-side compression engine. Unlike standard browsers that render web pages directly on the device, Opera Mini works as follows: