One of the lesser-known additions to iOS 14 is the option to set your default apps for email and web browsing from Apple's offerings. Chrome on iOS can already be your default browser, but some users seem to have issues where a bug resets it back to Safari when the iPhone restarts. Now, Gmail's newest version (ver. 6.0.200825) can become the default choice on iOS, too.
To make the switch, head to the settings page on your iPhone or iPad and select Gmail. From there, click the Default Mail App option and swap it from the default Mail app.
Source: Engadget