YaST is not comparable to yum or apt. YaST serves as a general OS configuration tool, sort of like "Control Panel" in MS Windows. While YaST can be used to install packages, packages can be retrieved from the command-line using "zypper" which functions similarly to apt-get and yum: http://en.opensuse.org/Portal:Zypper

I'm not really sure what you are referring to with "support". If you are referring to the sheer size of the community, Ubuntu does has a larger community and also benefits from the fact that most Debian-related/Ubuntu-derivative related docs/advice apply to Ubuntu as well. It looks like openSUSE has a fairly active community forum: http://forums.opensuse.org/english/