The ubuntu meta packages indicate which pieces of software are part of the supported Ubuntu system, we don't support syslog-ng (it's in universe) and by replacing syslogd with it you are choosing not to have a supported system.
The ubuntu meta packages indicate which pieces of software are part of the supported Ubuntu system, we don't support syslog-ng (it's in universe) and by replacing syslogd with it you are choosing not to have a supported system.