2. the player has no playable cards left in their hand (the card(s) are only for tribes which can no longer be legally placed)
I'm a newbie but let's see if we can cover when this could possibly happen...at least that any given tribe could "not be legally placed."
It can't happen because the tribe has all it's meeples on the map, because the game would be over.
So for it to happen the tribe would have to have NO tokens on the map except in places already at peace...and no regions available NEXT to places where they have tokens... and all the six entry places would have to be at peace...
Does that cover it? Those do seem like pretty unlikely events but not impossible. Still, connecting this AND having a hand with no cards but these does seem like a stretch. (Better save that "trade" card for a good time!).