Atomstack itself says: “The M50 laser module can be installed on any engraver model of the Atomstack A5 series and can be used without any additional setup.” and they say the opposite: “No, you need the board”
I tested it and the signals came in properly.
The 3pin cable fits in the 4 pin socket (look at the boards: the naming on the pins tell where to stick it in.)
In the other thread, they say: Yes, you can. The A5 board supplies 5A, the M50 needs about 3A, so this should be no problem too. https://forum.lightburnsoftware.com/t/replacement-head-for-the-a5-pro-40/51177/6
But Im still not quite sure if it will work over long time. (I´m actually waiting for my adapter board from china and I don´t dare to run it without and if the full capacity can be used without the adapter board…