Disable Google from exeptions, if Opera for Android has that option and / or Use F-Droid and AdAway.
I don't remember If needs Root.
There is no exception option on Android app.
Yes, there is no exceptions option...
I've just installed on Memu to test it and also have discovered features in ODesktop not in OAndroid and features in OAndroid not in ODesktop... ¿?
As haven't seen any ad in OperaApp nor in OMini, (I use mod Hosts file) probably using AdAway (Hosts file soft installer) will block ads also in Opera, it works for block ads in whole system.
If it's not a problem with Opera servers as mentioned above.