Perhaps because you have not configured a LDAP database yet?  Is there any 
configuration file(s) in /usr/lib/sasl2/ ?

I don't know anything useful about LDAP - I've never used it.

On Saturday, 25 June 2022 17:41:15 BST Alessandro Barbieri wrote:
> Do you know why if fail at loading the plugin ldapdb?
> 
> giu 25 18:27:16 ALESSAND-F1E8 syslog-ng[5921]:
> ldapdb_canonuser_plug_init() failed in sasl_canonuser_add_plugin():
> invalid parameter suppliedgiu 25 18:27:16 ALESSAND-F1E8
> syslog-ng[5921]: _sasl_plugin_load failed on sasl_canonuser_init for
> plugin: ldapdbgiu 25 18:27:16 ALESSAND-F1E8 syslog-ng[5921]:
> DIGEST-MD5 common mech freegiu 25 18:27:16 ALESSAND-F1E8 systemd[1]:
> Started System Logger Daemon "default" instance.