Based on the information provided in the extracts, it seems that Ory Kratos and your user interface must be hosted on the same top-level domain. This means that if your Ory Kratos is hosted on

<http://kratos.xyz.com|kratos.xyz.com>

, your user interface can be on

<http://ui.xyz.com|ui.xyz.com>

or

<http://xyz.com|xyz.com>

, but not on a separate top-level domain like

<http://abc.com|abc.com>

. Therefore, it might not be possible to enable users of

<http://xyz.com|xyz.com>

to sign in to

<http://abc.com|abc.com>

with the same credentials using Ory Kratos, as they are different top-level domains. However, for managing user identities across different applications within the same domain, Ory Kratos provides a robust set of features including self-service login and registration, multi-factor authentication, account verification, account recovery, profile and account management, and admin APIs. For more detailed information, you may want to refer to the [Ory Kratos documentation](https://www.ory.sh/docs/kratos/ory-kratos-intro) and [Ory Kratos API reference](https://www.ory.sh/docs/kratos/reference/api).

For multi-tenancy, you should use the [Ory Network](https://console.ory.sh). It is the only available option to have a multi-tenant Ory Kratos setup. It's important to note that it is not possible to self-host Ory Kratos as a multi-tenant service as its data model does not support this due to data, scalability, and operational complexity. You can find more information about this in the [Ory Kratos documentation](https://www.ory.sh/docs/kratos/guides/multi-tenancy-multitenant).

Yes, Ory Kratos does support Single Sign-On (SSO). It allows you to implement user management, login, and registration in a secure and straightforward way. Ory Kratos implements all common flows such as login and logout, account activation, multi-factor authentication (MFA), profile and session management, user-facing errors, and account recovery methods. For instance, you can set up an Ory Network project as an SSO provider that manages user identities and provides OAuth2/OIDC endpoints for authentication and authorization. This can be used by other Ory Network projects for "social" sign-in. This setup is described in the [Ory documentation](https://www.ory.sh/docs/kratos/social-signin/ory). Moreover, Ory Kratos also supports organizations, which are a way to group users within one project. An organization can have multiple OIDC SSO connections, and all members of an organization must use one of the organization's OIDC SSO connections to log in. This is explained in the [Ory documentation](https://www.ory.sh/docs/kratos/organizations). Please note that while Ory Kratos does support SSO, it must be hosted on the same top-level domain as your user interface.