Recently (years, not decades) LEGO introduced a new family of motors, sensors and control system – it was and is a bit confusing, but whether you think of LEGO WeDo, Control+, Powered Up, Spike Prime or the new Mindstorms 51515 it is all based around common backbone and, especially, a common connector – a 6-pole non-stackable plug.

Which, by sheer coincidence naturally, is completely incompatible with the old Power Functions connector from LEGO, who also claimed not to intend to manufacture an adapter cable because reasons.

Before someone jumps at me: I do understand WHY. And no, I don’t mean ‘to sell all motors again’. There is a technical reason not to make an adapter cable. You see, when the Power Functions system was designed, the main source of power was a dumb battery box. Even equipped with a cheaply made switch, a 6AA battery box can withstand all the power draw that stacked multiple motors can realistically take and it is the batteries that will fade before the box melts. With PoweredUp the world is a bit different. The basic box is a remote control receiver, so its outputs are electronically controlled. They have limited output power and for that reason it is necessary to limit the amount of power drains (motors) that can be connected to a channel. So they decided to limit it to one. I’d expect the lights to have a stackable plug though, as the LED lights take minimal power, but that’s a different story.

For all details see https://www.biasedlogic.com/index.php/lego-powered-up-connector/