Nothing new about Elby/Ken Stone. Ken's been a module designer for decades now, and has a history of adapting Serge circuitry for Eurorack purposes, as well as Elby's own "Euroserge" variants. Even other manufacturers use Ken's designs, such as Doepfer on their A-171-2.
FYI, if you expect to get Serge results out of 3.5mm jacked Eurorack, you're likely to be underwhelmed. Part of the Serge's appeal was the ability to branch signals off of a single patchpoint, because all points were banana jacks and therefore stackable. Typical Serge patches would sometimes output the same signal to several different destinations, which contributed to the "magic" of the format. As for interconnecting Serge with Eurorack, this is really simple, as Eurorack offers numerous banana-to-3.5mm adapter modules, plus there's standalone adapter boxes for this. But...VERY important...you have to establish a common groundplane between the Eurorack and "proper" Serge format gear, since the Serge relies on its own internal groundplane, and the patchpoints only connect "hot" input and outputs over a single conductor. It's easy enough...but necessary, as the two formats don't play nice with each other UNLESS they have a common ground.