Can my Tadelakt be finished Matte?Updated 2 years ago

No. 

The water-repellent seal of a Tadelakt Finish is dependent on a smooth finished surface.  Plasters that are matte tend to have a rougher texture and can present problems with moisture intrusion and mold growth in a wet environment like a shower.   In a non-wet area, Tadelakt could be applied with a matte finish.