Oidc: "Configured attribute users is not known."

Hi,
I am migrating OC 10.10 with openidconnect 2.1.1 to OIDC login with Keycloak as IDP. In the IDP login workflow I get

Configured attribute users is not known.

when the IDP redirects back to OC. The attribute is set in the openid-connect config key in the oc_appconfig table.

“search-attribute”:“users”

The OIDC mode from https://github.com/owncloud/openidconnect#all-configuration-values-explained is “userid” I dont understand why OC shows this error and owncloud.log has no info.

OIDC config: https://cloud.netzwissen.de/index.php/apps/openidconnect/config