You can only add 2 (TWO!) accounts for free before they charge you with a hefty subscribtion. Terrible, given other apps are literally FREE and give you unlimited accounts!
Thank you for your feedback, we understand that there are some free alternatives, however, all the free alternatives have their weak sides, specifically, no end-to-end encryption, no backup option, no desktop version, no browser extension, no guides on how to enable 2FA for specific services and most important no customer support. Our monetization helps us constantly improve the app and offer the best user experience possible in generating, managing and using Two-Factor Authentication (2FA) codes. Also, we would like to mention that Authenticator App is not just an app that generates codes, is much more, it's a security-related project that should guarantee users' privacy, and security and most importantly easy to use in daily tasks. I don't think the other Free alternatives can guarantee these concepts.