@an0nymous I checked all this page...and the only thing it worked is this link: https://www.reddit.com/r/operabrowser/wiki/opera/dark_mode_settings/

more specific: Opera GX also allows you to force pages into dark mode by applying its own dark theme to pages. To control this, there's a global "Force Dark Pages" option at the URL opera://settings/opera-gx. But, you can also override the global on a per-site basis by right-clicking a page and choosing "Force Dark Page" or "Disable force dark page". And, to get a view of all sites that are overriding the global, you can goto the URL opera://settings/content/forceDarkMode. Note though that forcing a page to be dark when a page is already displaying as dark because of its own theme and or an extension you have installed can cause page colors to look weird. So, if you have problems with colors, always check your dark mode extensions, the page's theme, and Opera's dark mode settings to make sure you're only using one method of darkness.