@john-phd i am going to post a tutorial on fixing your exact issue with opera audio since I had a copy of the exact same issue. If that's not enough for you, then I'm sorry. Then I guess you have no interest in knowing the solution to said problem.
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Go to the Microsoft store for reference. It's the little thing that looks like the windows logo on your taskbar. If you have deleted it, just search for it where it says type here to search. https://drive.google.com/file/d/1jqmtzfBOiuQJ6Wf4O5CUKCxqOcfS_i6g/view?usp=drive_link
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Search for the app called ear trumpet. https://drive.google.com/file/d/1gPkYJney0DZWAUyncBj0n4FleMKJRT21/view?usp=drive_link
then download the app called ear trumpet, https://drive.google.com/file/d/1YqP2NKi04SbruQCVxf2AW1LzwJwtz9wY/view?usp=drive_link
and finally USE the app called ear trumpet https://drive.google.com/file/d/1wRCys2VX7ZbXV75i2bgkxnyAebtRGMBo/view?usp=drive_link
Now that I have it all laid out for you (and even in video form no less), let's address your previous points.
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point number one is that your idea of it being an audio card issue etc. etc. is NOT the case as I've had the exact same issue down to the letter now. What you may ask is "then why are you using brave browser in your videos?" It is simply because I prefer brave over the other browsers out there currently and back when I found and tested this solution, I preferred opera.
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Now john, my own very valid point. This audio issue is in no way windows related. it is in no way audio card related. This is an opera issue. It cannot be fixed in the opera settings (I have tried). It cannot be fixed in windows sound settings (I have tried). It cannot be fixed by rebooting the computer (i have tried). Is there anything I'm missing? Heck, it's been awhile but I've probably tried that too ear trumpet was the only solution. If there are any more questions. I have even recorded videos laying out the steps for you if you ever want to simply try them again.
to end this little step by step tutorial for any future users who have this issue john, by the very fact that you have stated your field of expertise, most people will in fact infer that you are smart.
For those who have had this issue and still have this issue, this solution is for you. @NH2022 is the one who recommended it and it was only due to this I was able to diagnose and fix the problem, so all props go to him, thanks man 
As a side note, I wanted to add that if it were as simple as muting or unmuting the speaker from the task bar, I can say with 100% certainty that I would have figured out such a simple solution. But the opera audio bug is a hidden mute button that somehow gets activated accidentally, and the only way to enable it is by either downloading and installing ear trumpet or, as you have said, waiting several months after uninstallation for the problem to be solved. However, this solution is immediate, and the answer I'm assuming you have been curious about maybe? Not all software is the same. In all your knowledge thus far, This is one key factor you seem to be forgetting, and it has been the very thing that led you to waste your time on so many other posts instead of looking at the one halfway up this thread and just being done with it. You just chased a random rabbit instead for amusement, I guess? Oh well, moving on; at least it's here for others later on. Here's the solution to your problem (in the vast majority of cases relating to this issue, I would assume).
