Not sure if this is a specification or a problem, but I will report it.
I enabled the preempt_rt kernel with the following command.
sudo swupd bundle-add kernel-rt
sudo clr-boot-manager set-kernel org.clearlinux.preempt_rt.6.1.38-105
Then after rebooting, it failed to mount the rootfs and failed to boot.
Rewrite the entry in “loader/entry/Clear-linux-preempt_rt-6.1.38-105.conf” in bootfs as follows.