I can confirm that it works if done as described by @annoxedcustomer, but I had to use an 8GB stick in slot A1, it didn’t work with a 16GB stick.
I also had to turn sync off and on again in the web interface, but then it worked and the System-Inventory showed the right parts.
I hope this works for others as well, because than these boards are an amazing value since they can be had for 40-50€ new.