I agree, ceet12, those note add-ons are nothing like Opera's copy to note, not to mention some of them don't work at all for whatever purpose they were intended. Just because an add-on has "note" in the name doesn't mean it functions the same way as the old copy to note feature. If I wanted to use something like Google Keep, I would just use Chrome and I wouldn't need Opera. I use Firefox, Chrome and Safari already. If the notes function is gone, then I can just uninstall Opera and I won't lose anything.
And I also agree with you 100%, ceet12, in your use of the word "annoyingly" in your original post. On the Opera Help page it said: "During your upgrade, Opera 15 condensed your notes into an .html file, and saved them to your computer. Look for a file called Opera 12 Notes.html on your computer's desktop." I found that html file, but there was nothing in it. That was annoying. Luckily I found my notes at https://link.opera.com/notes/ but they aren't on my computer, as I have to sign in to Opera to access them instead.
In addition to "annoyingly," I would also use "sadly," because that's how I feel about losing this feature. I used to brag to my co-workers about how well Opera notes worked and how there wasn't another browser that had anything as fast and simple. Now it's gone without any warning or explanation, and we're plainly told it's not coming back. I guess there weren't that many people using the feature, judging from the half-hearted advice on where to find some similar app, coming from people who admittedly never used the function in the first place.