It look like lexel design the aux board to work with original fw3a driver which use 8 bit attiny85.
So, aux led is not support in anduril for that microncontoller. The aux led is not control b attiny, only by voltage. It look like loneoceans new lume 1 driver for fw3a support andril with aux led because it use different attiny. https://budgetlightforum.com/t/-/60947