turbo trainer

If you're on Sram AXS, then you actually need XDR, which is longer than standard XD. Tacx offer an XDR freehub body (an an XD one) for their direct drive trainers here: https://tacx.com/product/bodies-direct-drive-trainers/, though it may be a case of buying the trainer and the body and swapping yourself. Other manufacturers may offer similar items.

If you're not running AXS, then you don't necessarily need the XD body, because there are Shimano splined options available which are compatible with whatever cassette you're running. What drivetrain do you have?

Then you can run a Shimano, Sram, Sunrace or any other 11 speed 11-42 cassette. They all fit on a standard Shimano splined freehub and have the same spacing.

shewy wrote:

Are you saying I could fit an 11 speed 11-42 cassette on the trainer and fit my bike on and have no problem shifting?

Exactly. The cassette spacing is identical. There's a chance that the position of the cassettes won't line up perfectly, but it generally fits ok.