😃 May this produce joy for some!
#reverseengineering completed now by finding a pattern to light all six LEDs with 3 driver pins. I've put it into a drawing, together with a schematic: each driver pin is connected to four LED pins (two anodes and two cathodes). To leave an individual #LED dark, in its time slot leave one or both drivers high-Z.
They used 5V for the #microcontroller and blue LEDs, because of their forward voltage >2.5V.

They took 200µs per time slot: overall period of 1.2ms.