We are currently working on a replacement of a CEP extension, that is part of our DAM Platform vjoon seven.
This new UXP plug-in will listen to the document open and close events. Upon close, it will bring up modal dialogs to control the check-in process. We do not need a panel or command in any menu.
To do so, we need our UXP plug-in to be started automatically when Photoshop is launched. With CEP this is no problem.
Looking at your UXP reference for entry points, there are life cycle hooks on the plug-in level: ‘create’ and ‘destroy’. Neither of them seem to work (in UXP 4.1.x).
But Adobe has removed CEP capabilities from the latest version of Photoshop (Silicon), so our customers can’t use our integration with that version of Photoshop, and we must find a solution.
We looked at two workarounds:
 Use a menu command to “activate” our UXP plug-in. However, this does not make sense, as users will always forget to select this command upon launch of Photoshop and it would be a horrible UX.
 We add a dummy panel without any useful functionally which will be kept open. Once opened and maybe minimized, it will act as a starter of our plug-in upon launch of Photoshop. However, this is a hack at a level that we usually would not pursue.
So we need a proper solution urgently. Please tell us how our UXP plug-in can be activated upon the launch of Photoshop.
Looking forward to hearing from you soon.