Extension Manager is a no-go. Its support stopped with CC (2014 for what I remember but might be wrong with the date).
In any cases, you can't rely on this product unless you are still doing Flex based extensions fro CS5 to CS6 users.
Addons should be your favorite way of distribution but if you want to master the distribution by yourself, you have to have your users use the ExtensionManager CommandLine tool :
Or to create your own installer. I guess the Extension Builder forum will be more helpful on that matter.
Thank you, Loic.Aigon!
... have your users use the ExtensionManager CommandLine tool : Adobe Exchange
Not sure I want to “ship” with my own installer, considering that the only file being copied is the actual .zxp file. Bummer that Adobe seems to have abandoned their own extension manager.
I've used the ZXPInstalled without issue, but not very much.