You don’t have to wait for Android 10 (Android Q) to be available on your device to use the Dark Mode feature ?
Dark mode or night mode: allows you to apply a filter to the screen, minimizing visual fatigue and reducing the blue light emitted by the screen of your smartphone.

Supported Android
(4.1 and up)
Jelly Bean (4.1 – 4.3.1),KitKat (4.4 – 4.4.4),Lollipop (5.0 – 5.1.1),Marshmallow (6.0 – 6.0.1),Nougat (7.0 – 7.1.1),Oreo (8.0-8.1), Pie(9.0)

Download Night Mode Dark Mode Enabler [No Root] 10 APK

Night_Mode-10.apk