Integration in UCS
The SAML integration in UCS already exists since UCS 4.1. You can find the login mask here by default: https://ucs-sso.domainname/univention/saml/. The following link serves the metadata: https://ucs-sso.domainname/simplesamlphp/saml2/idp/metadata.php.
The UCS manual describes how to add service providers. For Office 365 and Google G Suite there are special connector apps in the Univention App Center, which create, modify and delete users.
Tip: You can make SAML login available under another link to enable outside access for example. The Univention Knowledge Base describes how that works.