Apologies to anyone who might end up here, or who finds this in feeds or search results.
I was able to replace the failed HDD with a new hybrid drive and install Mac OS Sierra Beta without a hitch.
Trying to install the Apple OS Sierra Beta led to a series of events that seems to have rendered my MBP inoperable.
Ubuntu OS 16.04, named Xenial Xerus, was released. Days later I've rebuilt my server to correct the fails of the upgrade.
The end of April snuck up on me this year, and I missed the launch count-down and everything. But on Sunday I was alerted that a new version of Ubuntu was available for installation.
I thought I'd try to give this new Apple ecosystem a try.
I finished the server OS update a few days ago, and all seemed to be going well.