It sounds like there may be an issue with how Opera is interacting with YouTube, especially if you're experiencing the same problem with another browser extension like DuckDuckGo. Since the videos load normally on other browsers like Firefox, Chrome, and Microsoft Edge.

It's likely not an issue with your internet connection or YouTube itself.
One thing you can try is clearing your browser's cache and cookies, as this can sometimes resolve loading issues. You can also try disabling any extensions or plugins you have installed in Opera to see if one of them is causing the problem.

If the issue persists, you may want to check for updates to Opera to ensure you're running the latest version, as well as reaching out to Opera's support team for further assistance. They may be able to provide more insight into what's causing the issue and how to fix it.