The Opera 48.0 Help page says
Settings > Preferences > Advanced > Network and uncheck "Enable automatic redirection".
But there is no such option!
Can you please tell me how exactly have you found this help page that says that? I am trying to reproduce but I don't see it if I open Help from within Opera 48.
Where I do see such suggestion it is on old Help pages for Opera 12 (Presto) - but you have to google that page up...