There is none. Other than upgrading, your options are to save in some other 3D format - eg, 3DS - and assign all materials manually in Artlantis 1, or to back-save to ArchiCAD 10, the last version capable of saving in Artlantis 1 format.
The plug-ins are developed by Abvent, with updates on their web site, but also bundled for our convenience by Graphisoft. Any questions about the add-ons, why they no longer support version 1, etc belong on the Abent Artlantis import plug-in forum:
We are in the same boat where we now have a redundant Artlantis Studio 1 We only had it for 2 year before it became redundant.
I'm reluctant to have to update software just to be able to read a newer format.
Perhaps GS should have included a translator for it or even better forced Abvent to make it available. Imaging if GS decided not to include a dwg translator.
Aziz Tayob Architects
AC23 INT rel 3003, OS X 10.14.6 iMac 3.3ghz i5 dual monitor, 24GB RAM