From your last post i can see that you are using an app version from the test app center (docker image url has docker-test.software-univention.de in its URI).
We are actively developing this app version and cannot support any app from the test app center - they are by definition in development status. You should use an officially released app version. Try installing the openid-connect-provider app version 0.7-beta, e.g. univention-app install openid-connect-provider=0.7-beta
edit In addition, openid connect is only one way to realize single sign-on with UCS, SAML is the other. Configuring additional service providers for the simplesamlphp Identity Provider is covered in our documentation.