Opera has a handful of different browsers for Android, each with a slightly different use case. Opera Touch is an experimental app, with a gesture interface reminiscent of Paranoid Android's "PIE' gestures from back in the day. If you're using the browser on Android 10, you might be happy to know it can now sync with the system theme.
Opera Touch already offered white and dark themes, but as of version 1.22, there's a new option to sync the browser with the system. No need to switch the browser's look manually at night, it will simply follow whatever the Android OS is using. The setting also appears to work with the system theme on Samsung OneUI devices.
Left: Light theme; Right: Dark theme
You can give Opera Touch a spin by downloading it from the widget below. We also have the APK on APKMirror, if that's more your style.