I am not sure what you need but my printer, bought about 2-3 years ago, has duplex printing and you find drivers in AUR. It is a Brother DCP-J562DW.
Thanks for the information. Unfortunately this printer is evidently not being made any more; at least it does not show up in Amazon.
It seems that there are a lot of Brother printers for which there are drivers in AUR. Possibly someone can inform me of a currently-available Brother color (preferably laser) printer which features duplex printing.