Hi Oliver,
It looks like RelyingPartyRegistrationRepository bean is not being created.
In Spring Boot, this bean is usually created automatically from the correct SAML properties. Please check that you are using the spring.security.saml2.relyingparty.registration.* properties and that cBioPortal is actually loading them.
See the cBioPortal docs here
https://docs.cbioportal.org/deployment/customization/security.properties-reference/#saml-configuration
If that does not help, try enabling more detailed Spring Security logs:
logging.level.org.springframework.security=TRACE
This should give more information about why the SAML registration is not being created.
I hope this helps.
Regards,
Ruslan,
SE4BIO