Since the official store link is dead, these third-party repositories host the last known versions for Windows Phone and Windows 10 Mobile: Opera Mini 9.0.0.211 XAP v8.0.0.6730 Winphone Iz Blog : Hosts the Opera Mini offline XAP/APPX files specifically for manual installation. Reddit Community Links : Users in the
Some older XAPs have expired certificates. You may need to set your phone's date back to 2015 or 2016 temporarily to complete the installation. opera mini xap for windows 10 mobile link