Finally got the dockerfile from the Linux Academy to successfully run on my Linux Mint computer by…Uninstalling the old then reinstalling docker. Followed this guide https://gist.github.com/dweldon/39ca0536168a92815a56df44eb55a337 which managed to accomplish the task in far fewer words than others I saw. Now at Docker version 19.03.5, build 633a0ea838! Wow that little diversion really slowed my Docker progress. However as usual solving problems causes you to dig deeper onto a subject!
Although upgrading fixed the problem I somehow feel there must have been some other underlying reason for the failure.