Thanks. My interceptor is running 5.15.32-v8. I assume you're cross-compiling on x86 for the Pi, so I should be able to pull 5.15.32 headers on the x86 system and build against those. I'll start in a VM and give that a try. Thanks!

I figured it out. cmdline.txt lives in the EFI partition created by the installer, which is not automounted. I mounted /dev/mmcblk0p1 to /mnt and added my parameters to /boot/cmdline.txt. Then rebooted. Now I can spin up a k3d cluster.