Casdoor is a promising open-source IAM solution: https://casdoor.org/ , written in Go and React. All features like OIDC, OAuth 2.0, SAML, CAS, LDAP, WebAuthn and 2FA are all supported. SaaS management is also supported like pricing, subscription etc.

Source code: https://github.com/casdoor/casdoor

Compared to Keycloak, Casdoor has:

1. Support high-concurrency and use less memory (Go v.s. Java)

2. More modern SPA-style web UI (with React and Ant Design), more CDN friendly

3. full-fledged RESTful API

4. Support a lot of provider types: OAuth, SMS, Email, CAPTCHA

5. More powerful authorization (powered by Casbin), Casbin is a popular authorization solution with a lot of integrations for DBs and applications: https://casbin.org/

SaaS hosting is also provided at: https://casdoor.com/ for anyone who don't want to self-host