If OIDC is not configured, slapd outputs startup error message from the SASL module "oauthbearer": === slapd[3966]: oauthbearer_client_plug_init() failed in sasl_server_add_plugin(): error when parsing configuration file slapd[3966]: _sasl_plugin_load failed on sasl_server_plug_init for plugin: oauthbearer === Even if it looks like this is fatal, it almost certainly is not the cause of whatever problem you are facing. It's just telling you that /etc/ldap/sasl2/slapd.conf doesn't contain any trusted idp config. slapd will still start, only the SASL module tells you that it will not be available.
https://github.com/cyrusimap/cyrus-sasl/blob/master/lib/server.c#L443-L449 > if ((result != SASL_OK) && (result != SASL_NOUSER) > && (result != SASL_CONTINUE)) { > _sasl_log(NULL, SASL_LOG_DEBUG, > "%s_client_plug_init() failed in sasl_server_add_plugin(): %z\n", > plugname, result); > return result; > }