You can enable it by following steps:-
STEP-1: Open the settings in WhatsApp
STEP-2: Afterthat select Chats option then you can Theme options under Display you will see three choice
1- System Default means when you switch to either darkmode or back to normal mode WhatsApp theme will work according to mode you switch.
2- Light theme even when you in darkmode and you want WhatsApp to stay in light theme.
3. Dark theme if you not switch to darkmode but WhatsApp stay in dark theme.
WHATSAPP VERSION
