If all my deployment groups are dead / exhausted already, does this timing instance still happen?

Context: Inspiring Leadership deck, Supervisory Agent. I want to know if I am required to play this card while I still have groups to activate, or can time it for a late deployment if everything else is already activated

Thanks!

No. You need to be able to activate a group to have a "before activating a group".

If you don't have a ready group, the play passes to the "other side".

(We have talked about this with the designers and another tech editor.)

Thanks, understandably as that would disallow "skipping" activation

Exactly, otherwise it could be used as the "pass rule" in skirmish.