Problem scenario
You are trying to install Linux SUSE. You get an error "The System cannot be installed because the following errors were found: There is no device mounted at '/'. How do you get passed this problem?
Solution
Use the "Expert Partitioner". Verify you have one device (e.g., /dev/sda1) that has the Type "BIOS Boot Partition." Verify you have one device (e.g., /dev/sda2) that has the Mount Point "/". You theoretically might be able to have one device have both traits.
If there is a device that is mounted to "/mnt", highlight it, go to Modify -> Edit Partition then go to the "Mount Point" and change it to "/". You may be prompted "Really skip formatting the partition?" Choose "Yes". Now try to resume the installation.
You may be prompted to abort the install or continue anyway to a variety of errors/questions. You may be able to just keep clicking "continue" through this series of prompts.