Checked it yesterday. It works great. The reason it wasn't working with the SE/30 was because the Bourns network filter is/was dying and thus the serial ports were sporadic. With the Duo, it tests just fine.

Here it is with my iBook G3 900MHz, running 10.2.8.



It works fine with 10.3.9 or earlier. It will not work with 10.4 or greater. You must have Classic AppleTalk services, which 10.4 doesn't have. You enable this in NetInfo Manager. Once that is done, simply set up the LocalTalk side with MacIP Server in TCP/IP, head to the Network control panel and select LocalTalk, set AppleTalk to Modem/Printer Port, then set the other side up correctly.