Macbook (8,1) Drivers for other Operating Systems
I don't think you're missing anything, no. The Retina MacBook 8,1 is not listed as a compatible hardware model for Ubuntu 16.04.

Indeed the Ubuntu bug tracker has open bugs for support for stuff like keyboard, touchpad and others:

TouchPad doesn't work

Keyboard doesn't work

The same issues exists in the Linux kernel bug tracker, so they might be generic Linux issues and not Ubuntu specific.

I have seen reports from others that sound is not supported and that the SSD is hard to get working.

So all in all, unless you're willing to put in effort to fix these issues yourself - it is probably not going to be a good experience running Ubuntu natively on the MacBook.

Instead you could look at virtualized options.