- Open chrome://flags in the Chrome app
- Search for the “Darken websites checkbox in themes setting” flag and enable it
- Relaunch Chrome
- Go to settings in chrome and select “Themes”
- There will be an option to “Darken websites” when you choose System default. Enable “Darken websites”
- Enjoy a more complete dark mode experience in Chrome
How to get full dark mode in Chrome in Android (Web pages and app theme) 2020

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Who cares.
It also works on other chromium based browser.