Unfortunately there isn’t a direct replacement for Posterize Time. The closest I’ve found is to use the FrameHold node.
First, on your Read Node set the After value for Last Frame to Loop.
Then for a bit of maths! Take your current frame rate (e.g. 24), divide it by the desired frame rate (12) and paste that value into the Increment value in FrameHold. As you can see it’ll only accept integer values.
Not an ideal solution but all there is until a Posterize Time feature is built!