Great points.

> and TOTP, the obvious alternative solution, is still pretty sorry. you have to download an app to do it, it's not just a capability that a phone has by default. and then when trying to find an app to use for it, you're presented with a multitude of high-stakes choices, and often pretty technical explanations if you start internet searching about which app to use.

A reminder that mandatory iOS App Store / Android Play Store / (Xiaomi store ???) is even less acceptable than SMS 2FA unless maybe you're a USA(/Chinese) citizen living in USA(/China).