Google has been recently updating many of its apps with Dark Mode UI. Google app, Files, Google Drive, and Google Keep have recently started receiving Dark Mode, albeit not all of them have received it in all the markets.
Now, as reported by Android Police Google may have started shipping first instances of Dark Mode in Gmail for Android. The latest Gmail APK has Dark Mode only in its settings but it reflects on Google’s plans to bring the Dark Mode to Gmail. Check the screenshots in the featured image above.
If you want to feel it yourself you can install the APK from here. But it seems there is no toggle for switching it on and off. It is only in settings and doesn’t appear in the main Gmail UI anywhere. The Gmail version in question is v2019.06.09.