[pelagicAustral]

I’m curious to know if there are any oss alternatives for similar services.

[wg0]

Ory, Keycloak, Authelia and bunch of others come to mind if that's exactly what you're looking for.

[nailer]

If you just need oauth2 + openid connect, you can install a library from your Open Source package repository of choice.

[dt3ft]

keycloak