Authentiq - Strong authentication, without the passwords
TypingDNA Authenticator - 2FA codes in your browser, secured by the way you type
Cotter - One-click phone number login and checkout
PropelAuth - PropelAuth hosts and manages your authentication.
SuperTokens - Open Source User Authentication - An Alternative to Auth0 / Firebase Auth / AWS Cognito
Authorizer - Authorizer is an open-source authentication and authorization solution for your applications.