Hi @Galochka, sorry for the late response here.
Xperia phones on Android 9 don't support Dark mode on system level, but some third party apps have implemented Dark mode in certain apps such as Instagram. If you want to turn Dark mode on or off in a specific app, please check the Settings section in the app. Depending on how the app developer has implemented the feature, it might not always be possible to manually turn Dark mode on or off. For more information and detailed support, please contact the app developer.
I hope that helped! Let me know if you have any further questions!
