Wasn't it Dgates who wrote:

So, as I work through this, I'm forming the opinion that the second
player will win. The second player will quickly put a checking piece
right next to any king on the board, then ensure that the checking
piece can be captured.

Once the second player has stuck a white queen right next to the black
king, and positioned a black rook right next to the white queen so
that it can capture the white queen, there's no way to add an
additional checking white piece without creating an illegal position.

So, if Player 1's first move is the black king, then Player 2 counters
by putting the white queen right next to it.

I can't see how the second player gets time to place the black rook next
to the white queen.

I see the game going like this

Me: Black king in a corner
You: White queen right next to it
Me: White rook defends the white queen: checkmate

The position conforms to the requirement of being "legal (or able to be
made legal by adding the missing king(s) to (a) suitable square(s))".

--
Mike Williams
Gentleman of Leisure