We know Android 10 and Samsung One UI 2.0 fully support dark mode but the issue is a few major apps such as WhatsApp and, ironically Google app itself, are not implementing the dark mode.
Suggested two-step workaround :
1. Use beta versions of WhatsApp and Google which support dark mode;
2. That may still leave you with Google search engine Chrome still not in dark mode. For dark mode in Chrome use one of the experimental options (chrome://flags) to force dark mode.
I've checked, yes you are right. Latest version of WhatsApp in Play Store, version 2.20.64 released 2 March 2020, supports dark mode - the first official version to do so.
In my case I had WhatsApp dark mode much earlier when WhatsApp version 2.20.64 was still in beta phase, and I continue to get beta version updates. For example my current WhatsApp is version 2:20:85 beta released on 14 March 2020.
So as WhatsApp beta user, I overlook the fact that the official version has already gone dark so to speak.
