@GuidoCazzaniga Actually, there's no reader mode in Opera on iOS. On Android you have this, yet.
With the web going more mobile first, there shouldn't be a thing about it, as Opera frees you from most of the ads on a web page.
If you heavily rely on the option to have a reader mode, you should either stick to Safari which has. Or try Edge or Brave which also have decent ones.
From my personal experience I don't need it on my iPhone. And even on desktop I use it only for very long text.