TypingDNA Authenticator - 2FA codes in your browser, secured by the way you type
Authentiq - Strong authentication, without the passwords
Cotter - One-click phone number login and checkout
Auth0 - Auth0 is a program for people to get authentication and authorization services for their own business use.
SuperTokens - Open Source User Authentication - An Alternative to Auth0 / Firebase Auth / AWS Cognito
Authgear - Authgear offers developers a simple, secure, and scalable User Management Solution for web and mobile apps.