I had to wait a long time
While for Android, Google tried to quickly add a dark theme for most of its core services, with iOS, everything is a little off.
Gmail
IOS users finally get a dark theme for Gmail
Only now the Gmail application for this operating system has got a dark theme. Given the popularity of iOS, dark themes, and Gmail, it’s not clear why Google has been pulling for so long, but the wait has finally ended.
Updating Gmail for iOS brings support for the system dark mode, so you won’t need to enable anything separately, although there is such an opportunity. Interestingly, Dark Mode is not mentioned in the update description. But it says support offline search.