Hello, I'm also interested in this Opera GX on Linux topic. I've seriously considered starting to use a Linux distribution called Nobara, but on Windows, I've already become too accustomed to Opera GX and I don't think I can use any other browser.
I hope that in the future they develop an installer or put the app in some repository for download on Linux, but until then, I think I found an option.
Researching around, I found out that Opera GX is available for download through the Epic Games Store, and I'm not sure if anyone has tried it yet, but maybe someone can use Lutris or Heroic Games Launcher to access the Epic Games Store and from there to Opera GX.
If anyone has already tried it or has the possibility to do so, please tell us how it went to see if it works.