I think there used to be a Mouse Cursor section in chrome://settings/content in Chromium browsers where you could get to the allow list. But, that's gone now it seems. And, with Chrome, it no longer seems to ask you if you want to allow the hiding/disabling of the mouse cursor. It just automatically allows it. However, Opera still prompts you.

So, I'm guessing Opera's custom prompting relies on adding to the allow/block list which is no longer supported by the underlying Chromium. I'm then guessing that until things are sorted out by Opera, you'll always have to click "allow".

Looking forward for an early fix.
Thanks