Tried on a sle15-sp6 with latest kernel. Already the setup fails.

I'm using this doc:
https://documentation.suse.com/sles/15-SP3/html/SLES-all/cha-tuning-kexec.html#cha-tuning-kexec-basic-usage

localhost:~ # systemctl enable kexec-load.service
Created symlink /etc/systemd/system/kexec.target.wants/kexec-load.service →
/usr/lib/systemd/system/kexec-load.service.

localhost:~ # systemctl start kexec-load.service
Job for kexec-load.service failed because the control process exited with error
code.
See "systemctl status kexec-load.service" and "journalctl -xeu
kexec-load.service" for details.

localhost:~ # systemctl status kexec-load.service
× kexec-load.service - load default kernel into the current kernel
     Loaded: loaded (/usr/lib/systemd/system/kexec-load.service; enabled;
preset: disabled)
     Active: failed (Result: exit-code) since Fri 2024-05-17 13:28:02 CEST; 8s
ago
       Docs: man:kexec(8)
    Process: 11464 ExecStart=/usr/sbin/kexec-bootloader (code=exited,
status=203/EXEC)
   Main PID: 11464 (code=exited, status=203/EXEC)
        CPU: 532us

Mai 17 13:28:02 localhost.localdomain (otloader)[11464]: kexec-load.service:
Failed to locate executable /usr/sbin/kexe>
Mai 17 13:28:02 localhost.localdomain (otloader)[11464]: kexec-load.service:
Failed at step EXEC spawning /usr/sbin/kex>
Mai 17 13:28:02 localhost.localdomain systemd[1]: Starting load default kernel
into the current kernel...
Mai 17 13:28:02 localhost.localdomain systemd[1]: kexec-load.service: Main
process exited, code=exited, status=203/EXEC
Mai 17 13:28:02 localhost.localdomain systemd[1]: kexec-load.service: Failed
with result 'exit-code'.
Mai 17 13:28:02 localhost.localdomain systemd[1]: Failed to start load default
kernel into the current kernel.

localhost:~ # journalctl -xeu kexec-load.service
░░ The job identifier is 3360.
Mai 17 13:28:02 localhost.localdomain systemd[1]: kexec-load.service: Main
process exited, code=exited, status=203/EXEC
░░ Subject: Unit process exited
░░ Defined-By: systemd
░░ Support: https://lists.freedesktop.org/mailman/listinfo/systemd-devel
░░ 
░░ An ExecStart= process belonging to unit kexec-load.service has exited.
░░ 
░░ The process' exit code is 'exited' and its exit status is 203.
Mai 17 13:28:02 localhost.localdomain systemd[1]: kexec-load.service: Failed
with result 'exit-code'.
░░ Subject: Unit failed
░░ Defined-By: systemd
░░ Support: https://lists.freedesktop.org/mailman/listinfo/systemd-devel
░░ 
░░ The unit kexec-load.service has entered the 'failed' state with result
'exit-code'.
Mai 17 13:28:02 localhost.localdomain systemd[1]: Failed to start load default
kernel into the current kernel.
░░ Subject: A start job for unit kexec-load.service has failed
░░ Defined-By: systemd
░░ Support: https://lists.freedesktop.org/mailman/listinfo/systemd-devel
░░ 
░░ A start job for unit kexec-load.service has finished with a failure.
░░ 
░░ The job identifier is 3360 and the job result is failed.