Authelia is an open-source authentication server and portal for single sign-on (SSO) and multi-factor authentication. It acts as an extension of a reverse proxy such as nginx, Traefik, Caddy or HAProxy and protects web applications with access rules by subdomain, user, group or network. It supports OpenID Connect 1.0, time-based one-time passwords, FIDO2/WebAuthn security keys, passkeys and Duo push notifications, as well as self-service password reset. Authelia is delivered as a binary, a deb package or a container, and you run it on your own servers.
Authelia is a community project. According to its own website it is not a company or any other incorporated entity; it is maintained by volunteers. Its GitHub organisation lists Australia as its location, and several core maintainers list Melbourne. The source code is licensed under Apache-2.0. Because you host Authelia yourself, sign-in data and sessions stay on your own infrastructure; the developers do not offer a hosted service.