I bought the LED panel from AliExpress, this one specifically: https://www.aliexpress.com/item/Indoor-P7-62-LED-Module-244mm-x-244mm-32x32matrix-1-16-Scan-SMD3528-LED-for-7/32730524423.html
Although the images for the panels on that page show a 'D' pin on the header...
I was aware that all these panels can have a slightly different pin layout, but I didn't expect to receive one without all the regular connections!