It does appear as though Ubuntu is not supported by the Dell OpenManage software, but if you can manage to come up with the RPM files that would be needed for your server, you could try to use alien to convert them to DEBs and attempt to install them. However, this probably won't work, or at least won't completely work.
However, if you don't have dedicated RAID hardware, you could try to use mdadm for software RAID within the OS. If you can't use the Dell software, and this setup would be acceptable, you could easily use mdadm to monitor the health of the array.