The most popular apps like YouTube and Twitter already supporting dark mode feature in it, but WhatsApp is not yet. Developers of whatsapp said that users will have to wait a little more longer for it.
So that miui theme developer Ultra n00b is designed a darkoid theme which makes the whatsapp in dark mode. Not only for whatsapp but also for message app, dailer, status bar, settings and many more etc… This theme also supported for 19:9 screen ratio mobiles of miui 9 and 10 with a 100+ New Icons.
Click Here to download :- Darkoid
For more information visit this site