authentik is an open-source Identity Provider focused on flexibility and versatility. You can use authentik in an existing environment to add support for new protocols. authentik is also a great solution for implementing signup/recovery/etc in your application, so you don't have to deal with it.
For bigger setups, there is a Helm Chart [here](https://github.com/goauthentik/helm). This is documented [here](https://goauthentik.io/docs/installation/kubernetes/)