@leocg
How?
I have the same question as the OP but for different extensions. I've been looking for days and keep running around the same circles. It's supposed to be simple and direct, but what I am directed to does not exist.
The Opera Help page, https://help.opera.com/en/latest/customization/, says the Install Chrome extensions addon is required. But there is nothing by that name in the Opera Addons Store. Other sources, like you, @leocg, say or imply that this addon is not required, just click the Add to Opera button. in the Chrome Web Store. But I don't find any such button. The Chrome Web Store page says, for every extension I try, "To add this item to Chrome, please update your browser." But my Opera is up to date.
Has the most recent Chrome update broken this functionality such that the Chrome Web Store now requires something from the browser that Opera is not (yet) providing?
macOS Monterey
Version 12.7.6
Opera Version:83.0.4254.27 (x86_64)
Opera is up to date