This forum is only for reproducible bugs with csf and lfd (i.e. not iptables problems, lack of understanding how to use a feature, etc). Posts must be accompanied with full technical details of the problem and how it can be recreated. Any posts not adhering to this, or not considered bugs, will be moved to the General Discussion (csf) forum.
In my testing I wasn't able to get the MESSENGERV3 to work correctly on Debian/Ubuntu servers (It can't find the SSL certificates). It looks like there is a bug in the Messenger.pm conftree function because it can't process the relative includes used by default on Debian/Ubuntu.
# Include generic snippets of statements
IncludeOptional conf-enabled/*.conf
# Include the virtual host configurations:
IncludeOptional sites-enabled/*.conf
Changing the IncludeOptional lines in /etc/apache2/apache2.conf to the full path fixes the issue and all the SSL certificates are found properly like on Centos/RHEL/Cloudlinux. I think the simplest fix would just to alter the conftree function to detect if the include line starts with a leading slash and if not just prefix them off the /etc/apache2/ directory.
One last thing that I also noticed was that there seems to be an extra slash in the lfd messenger v3 log with the defaults (Although it doesn't seem to cause any problems):