Why does sssd return SID numbers instead of group names on Ubuntu?

I'm trying out sssd to use krb5 for authentication on a Ubuntu 18.04 host and can't figure out how to show the actual user groups (groups shows some sort of Windows SID instead of human readable names). The primary group looks ok (Domain Users...) but the rest (supplementary) are all S-x-x-x numbers. Is this an AD setting or something with my sssd config?

$ groups
Domain [email protected] [email protected] [email protected]...

sssd.conf

[nss]
   filter_groups        = root
   filter_users         = root
   reconnection_retries = 3

[pam]
   reconnection_retries = 3

[sssd]
   domains              = ad.mycorp.com
   config_file_version  = 2
   services             = nss, pam
   reconnection_retries = 3
   sbus_timeout         = 30

[domain/ad.mycorp.com]
   ad_domain            = ad.mycorp.com
   krb5_realm           = ad.mycorp.com
   realmd_tags          = manages-system joined-with-adcli
   cache_credentials    = True
   default_shell        = /bin/bash
   fallback_homedir     = /home/%d/%u

   krb5_store_password_if_offline   = True
   use_fully_qualified_names        = True

   ldap_sasl_authid     = UBU-TEST1$
   ldap_id_mapping      = True

   access_provider      = ldap
   id_provider          = ldap
   auth_provider        = krb5
   chpass_provider      = krb5

   ldap_uri             = ldaps://ad.mycorp.com
   ldap_search_base     = ou=mycorp,dc=mycorp,dc=com
   ldap_tls_cacert      = /etc/ssl/certs/ca-certificates.crt
   ldap_tls_reqcert     = allow
   dns_discovery_domain = ad.mycorp.com

   ldap_user_search_base   = ou=userid,ou=mycorp,dc=mycorp,dc=com
   ldap_group_search_base  = ou=mycorp,dc=mycorp,dc=com
   ldap_user_object_class  = user
   ldap_user_name          = sAMAccountName
   ldap_user_fullname      = displayName
   ldap_user_home_directory = unixHomeDirectory
   ldap_user_principal     = userPrincipalName
   ldap_group_object_class = group
   ldap_group_name         = sAMAccountName

   ldap_schema                = rfc2307bis
   ldap_access_order          = expire
   ldap_account_expire_policy = ad
   ldap_force_upper_case_realm = true

This is a bit old but I thought that I would share the solution that worked for me.

I solved this by adding a line to the sssd.conf file, in the [domain/example.local] section :

ad_server = <domain controller name>.example.local

and keep

ldap_id_mapping = True