A few days ago, the content blocker problem also became my problem. Today I found a solution for disable this content blocker in opera for windows. You need to create a shortcut with the parameter "--allow-running-insecure-content" Opera launches with this parameter does not block http elements on https pages. Unfortunately, I do not know how to do it for one website/domain only. For myself, I created two shortcuts, one with the blocker enabled and the other with disabled.
Three years have passed since your question but I have not found any answer so I answer 🙂0_1535397818970_opera.PNG