Wahoo KICKR 2018 and Shimano Sora 11-32t 9-speed compatibilty
Your bike should be compatible per wahoo:
"The KICKR uses an 11-speed compatible Shimano freehub body, but you can install an 8, 9, or 10 speed cassette with the proper spacers."

https://support.wahoofitness.com/hc/en-us/articles/204281874-Difference-between-10-speed-and-11-speed-KICKRs-

You should be fine installing the 1.8mm spacer on the kickr along with a 9-speed Shimano cassette. The same spacer is needed for installing 10-speed Shimano cassettes. Just make sure there is no play in the cassette after installing, if there is, you should be able to get different sized spacers from any bike shop as needed.