For those of you trying to get QuickTab to work from one of the Github repos, there is a good step by step flow documented in the Issues of the zendesklabs/QuickTab Github repository that worked for me.

Download the QuickTab repo from TymeShift's Github repository: https://github.com/Tymeshift/QuickTab
Unpack the zip file
Unpack the zip file from the releases folder
Open chrome://extensions in Google Chrome
Drag the unpacked folder structure into a your Chrome window

This works today, but since this seems to be in transition to TymeShift, I'd expect this to hopefully move back to the Chrome web store, but for now the two repositories are the same code.