Einrichten des HTTP-Servers:

https://documentation.suse.com/de-de/sles/15-SP5/html/SLES-all/cha-deployment-prep-uefi-httpboot.html#httpboot-http-server

Is the grub config correct?

timeout=60
default=1

menuentry 'Installation IPv4' --class opensuse --class gnu-linux --class gnu --class os {
    set gfxpayload=keep
    echo 'Loading kernel ...'
    linuxefi /sle/boot/x86_64/loader/linux install=http://www.httpboot.local/sle
    echo 'Loading initial ramdisk ...'
    initrdefi /sle/boot/x86_64/loader/initrd
}

menuentry 'Installation IPv6' --class opensuse --class gnu-linux --class gnu --class os {
    set gfxpayload=keep
    echo 'Loading kernel ...'
    linuxefi /sle/boot/x86_64/loader/linux install=install=http://www.httpboot.local/sle ipv6only=1 ifcfg=*=dhcp6,DHCLIENT6_MODE=managed
    echo 'Loading initial ramdisk ...'
    initrdefi /sle/boot/x86_64/loader/initrd
}

On fresh SLE15 servers "linuxrdefi" and "linuxefi" is not used anymore. 
Just "linux" and "initrd":

### BEGIN /etc/grub.d/10_linux ###
menuentry 'SLES 15-SP5'  --class sles --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-simple-279e96ed-f4bf-45f8-b526-70b0c200a02b' {
	load_video
	set gfxpayload=keep
	insmod gzio
	insmod part_gpt
	insmod btrfs
	set root='hd0,gpt2'
	if [ x$feature_platform_search_hint = xy ]; then
	  search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt2 --hint-efi=hd0,gpt2 --hint-baremetal=ahci0,gpt2  279e96ed-f4bf-45f8-b526-70b0c200a02b
	else
	  search --no-floppy --fs-uuid --set=root 279e96ed-f4bf-45f8-b526-70b0c200a02b
	fi
	echo	'Loading Linux 5.14.21-150500.53-default ...'
	linux	/boot/vmlinuz-5.14.21-150500.53-default root=UUID=279e96ed-f4bf-45f8-b526-70b0c200a02b  ${extra_cmdline} splash=silent mitigations=auto quiet security=apparmor crashkernel=363M,high crashkernel=72M,low
	echo	'Loading initial ramdisk ...'
	initrd	/boot/initrd-5.14.21-150500.53-default
}