First, I used the "kernel" component for filing this issue, but I think this is
a bug more somewhere in dracut/udev/systemd.

Reproduce this:
Take Leap 15.2 with current patches as of 16-nov-2020, take the current Leap
kernel source which is 

linux-5.3.18-lp152.50 

and take the Leap 15.2 kernel config from 

/boot/config-5.3.18-lp152.50-default 

in other words, use the standard Leap 15.2 kernel config and sources, no
modifications and build the kernel. 

You get the same kernel as shipped with Leap 15.2 which is 
/boot/vmlinuz-5.3.18-lp152.50-default

And now, when booting, the boot process will hang somewhere with this error:

dracut-pre-udev modprobe Error could not insert dm_mod : Operation not
permitted
--------------------------------------------------------------------------------


This looks as you can���t build a kernel on Leap 15.2 with software versions as
of 16-nov-2020. Maybe udev, systemd?

The kernel built process just works fine, everything builds, mkinitrd ran fine,
all modules built, no error.

But, when booting, no modules can���t be loaded, boot hangs.

I think building and booting a kernel from stable Leap versions should always
work, don���t know if you would consider this critical.