It seems the recent announcement of Civ7 has not stopped the new challenges!
The new Civ6 monthly challenge, going from July 16 until August 14 is: Live Yongle Reaction.
You play as the one and only, obviously, on a tiny fractal map on online speed. As usual you get to choose between Prince and Emperor difficulty, and also between a culture or science victory. For more information please check this thread.