So far as I can tell these are the things that you can't option on to Premium Plus that were on the Prestige:
Audi Adaptive Cruise Control w/Stop & Go
Audi Active Lane Assist
Heated Power-Folding Exterior Mirrors
High Beam Assistant
3D Optic Inlays (interior trim)
High-Gloss Aluminum Window Surrounds (exterior trim)
Interior Storage Package
Oddly the Technology page still has a couple of references to the Prestige trim: https://www.audiusa.com/models/audi-a3- ... technology. I think it's a bit dubious for them to advertise Lane Assist on the main A3 E-Tron page, but make it exclusive to a trim that they've removed from said page.