I know this plugin is marked deprecated, but I would not expect outright breakage with as widely as it is used. 

Current behavior is that it displays in the UI, but choosing an SCM from the 'Add SCM' dropdown doesn't seem to do anything at all. No error in javascript console, and no obvious change to the UI. 

Known to be working on a 2.263.x instance, known to be failing on multiple 2.277.x instances. 

I saw another issue with a report that there were problems with the UI display on 2.277, which I have noticed, but never noticed the breakage in adding an SCM until now.