Authentik is an open-source identity provider you can host yourself.
It lets you use a single login across your self-hosted services, with support for OAuth2, OIDC, SAML, LDAP, and more.
Useful for managing access to apps like Jellyfin, Immich, Nextcloud, Vaultwarden, and other self-hosted tools.
GitHub: https://github.com/goauthentik/authentik
More details: https://digitalescapetools.com/tools/tool.html?id=authentik
More privacy-friendly tools: https://digitalescapetools.com/
Been using it for our whole company of about 25 people max at one moment, it really is grwat, especially the group based authorization where I differentiate between people who have access to all apps versus those who just need one (like externists from other companies so they can view tickets in our OpneProject).