The submission is bullshit. I was denied submission because allegedly my extension was only pointing to a website (lets ignore the fact you can't create a login for it because it's using special client side encryption -> ProtonMail). Also lets ignore the fact it was designed to always open new tab no matter what page you had open, it would open a new tab and load the login form for ProtonMail. And final nail in the coffin that pissed me off is the fact that people have such extensions on fucking Opera Addons page that literally just load a webpage, but mine was denied because "reasons". And all this time no one gave ANY frigging reply for weeks. I was just waiting like retard until I got pissed off and started demanding answers and then someone arrogantly said it was denied because it's "just a link". Bullshit. Now I have to host the damn thing on my site and I basically stopped using it because I use it as a bookmark now and have to always specifically open an empty tab for it. Anyway, rant off, I'm surprised Opera Addons page isn't more dead given how shitty their support and submission process is.
See this FYI from Opera about the long approval time. Hopefully Opera will sort that out. https://forums.opera.com/post/128215
Is this the Firefox version you're talking about? https://addons.mozilla.org/en-US/firefox/addon/easy-youtube-video-download/
If so, you can keep an eye out in https://chrome.google.com/webstore/category/extensions for the Chrome version, which you can install in Opera using the method I mentioned previously. I don't see it in the Chrome web store yet, so have the FYI you when it's ready.