The trouble is the "Remote Disc" device was not showing up on my old Mac Mini's (broken DVD drive) and although I can usually avoid it I recently wanted to install something from a DVD. This machine has a DVD drive which is presumably why the option did not show up in the Finder preferences under Sidebar.
Fortunately these preferences can be turned on with a command line as follows:
defaults write com.apple.NetworkBrowser ODSSupported -bool true
defaults write com.apple.NetworkBrowser EnableODiskBrowsing -bool true
Enter that in the terminal and then Restart Finder using the Force Quit menu so the settings take effect.
Then you should see the remote disc icon and can mount remotely shared DVDs and CDs. Note that you must also enable DVD/CD sharing on the machine with the disc.
