CentOS 8.2 LDAP client configuration
sssd does not support LDAP authentication over unencrypted connections.
From sssd-ldap(5) man page:
If you want to authenticate against an LDAP server either TLS/SSL or LDAPS is required. sssd does not support authentication over an unencrypted channel. If the LDAP server is used only as an identity provider, an encrypted channel is not needed. Please refer to “ldap_access_filter” config option for more information about using LDAP as an access provider.