User said they changed clients and now saw UIDs in place of usernames. At first I thought it was a client issue, as it turns out, it is a client issue on how it’s requesting data. Unfortunately, the client was not smart enough to know the syntax was wrong with the new command set. proftpd has a setting to disable the list of modes it supports, so the client establishes the connection with the older command set. Here is the information on the switch.
Syntax: FactsAdvertise on|off
Default: FactsAdvertise on
Context: server config, ,
Compatibility: 1.3.2rc2 and later
The FactsAdvertise directive is used to control whether the mod_facts module advertises its MLST support via the FEAT command.
By default, the mod_facts module will list MLST in the FEAT response. FTP clients use this to determine whether to use the newer MLSD/MLST commands, or the older LIST/NLST commands. Some FTP clients, though, will attempt to use the newer commands just as if they were equivalent to the older commands, including supporting glob/wildcard characters. Section 2.2.2 of RFC3659 explicitly states that wildcard characters are not supported in the MLSD and MLST commands. Thus, to prevent problems when using such FTP clients with proftpd, you can disable the advertising of support for those commands using e.g. the following in your proftpd.conf: