You wouldn’t be able to use AdGuard properly with Opera anyway because Opera don’t accept user certificates (issued by AdGuard or AdAway) so it wouldn’t filter https traffic.
Try Vivaldi, amazing browser, built-in adblocker. Hopefully will be better than Opera’s. Personally haven’t tested it as I’m using said AdGuard which Vivaldi has no problem with - one of the reason I moved from Opera to Vivaldi.