I’ve had good experience with Gutterman TERA 80 on a wide variety of fabrics and it works fine on 200d fabric like the Dyneema X. You probably wouldn’t want to use anything lighter than this, but unless your friend is using an industrial machine (or knows otherwise) I would also stay away from the really heavy threads like a TERA 40 or DB-92. These threads are very strong and appropriate for heavy duty fabrics, but they’ll jam up most home machines, or you’ll never get the tension right.
I wouldn’t say there’s any special considerations sewing Dyneema X, just be sure to use sharp scissors or a roll cutter to get through the grids.