Looks like this was fixed in today's 66.0.3515.36 update.
Best posts made by aaronmalone
Latest posts made by aaronmalone
RE: [Solved]Display problems with extensions (they lost went pale)Opera for Mac
Prevent click on unfocused window from passing throughOpera for Mac
If my Opera window is not focused (that is, in the background), and I click on it to raise/focus the window, that click also gets passed through to the window. This is inconsistent with normal behavior on Mac, and is particularly frustrating if I have a full-content-frame video playing which pauses when I click to foreground the window.
I feel like I've looked through every config option and flag, but I can't find any way to disable this, or anyone else having mentioned it. Is there any way to turn off this behavior so that a click will just focus and raise the window?