Thanks for all replies!
I think i have to tell some more facts about my bike setup, which i should have done from the start. Sorry for that misstake! The question remains the same anyway:
Is there a completely slick trainer (or road) tire available for 650B rims. I think there will be because of the "650B-boom" there is for the moment. But who wants to wait?!
I know that any kind of pattern will create a lot of additional sound on the trainer, so i prefer a completely slick tire.
Frame, Scott Scale 700 RC with X-12 142x12mm through axle for the rear hub.
Wheel: DT Swiss 240S X12 with XX1 body and NoTubes Crest 650B rim
Drivetrain: Sram XX1 11 speed
Very unnecessary and expensive setup for a trainer, yes.
But my intention is only to get this build working on a trainer for warm ups, threshold tests, component tuning, etc. I normally use my road bike for indoor sessions.
A road wheel would probably work if it wasn't for the X-12 through axle. And i'm not sure if the index for an Sram 11 spd road cassette is the same as for the XX1?!