This happened to a family member who primarily used Gmail on their LG Sunrise candybar phone and never had 2FA enabled on the Google account. After an iPhone u

This happened to a family member who primarily used Gmail on their LG Sunrise candybar phone and never had 2FA enabled on the Google account. After an iPhone upgrade and SIM swap, they couldn’t login to Gmail on an unrecognized device because the only option for verification was to “open the Gmail app on your LG sunrise”. No 2FA enrollment ever took place, therefore no SMS fallback, recovery codes, or recovery email were offered as backup methods. By sheer luck we found an old laptop where Gmail was used recently enough to recognize the browser. At that point, only after removing the LG phone from “Account > My Devices” was it possible to enable 2FA and enroll a new iPhone as usual. This “silent opt-in” (without 2FA) of the phone’s Android Gmail app as the only way to confirm unusual logins is likely limited to a subset of low-tech users / low-end devices who missed the Google account security checkup prompts.