[Android Software Development] ace2nutzer:
Sure, kernel-image is gzip, there is even no option in defconfig to change it in 64-bit kernels .... dunno why.

Well, ramdisk repacked with LZ4 doesn't boot. :(

I did this change in kernel

and in "split_img/boot.img-ramdiskcomp" simply changed from gzip to lz4.

Output of AIK-Linux script:

LZ4:

Android Image Kitchen - RepackImg Script
by osm0sis @ xda-developers

Warning: Overwriting existing files!

Packing ramdisk (as root)...

Using compression: lz4

Getting build information...
kernel = boot.img-kernel
cmdline =
board = SRPPK02A010KU
base = 0x10000000
pagesize = 2048
kernel_offset = 0x00008000
ramdisk_offset = 0x01000000
second_offset = 0x00f00000
tags_offset = 0x00000100
os_version = 9.0.0
os_patch_level = 2021-01
hashtype = sha1
dt = boot.img-dt

Building image...

Using format: AOSP

Appending footer...

Using type: SEAndroid

Done!

GZIP:

Android Image Kitchen - RepackImg Script
by osm0sis @ xda-developers

Warning: Overwriting existing files!

Packing ramdisk (as root)...

Using compression: gzip

Getting build information...
kernel = boot.img-kernel
cmdline =
board = SRPPK02A010KU
base = 0x10000000
pagesize = 2048
kernel_offset = 0x00008000
ramdisk_offset = 0x01000000
second_offset = 0x00f00000
tags_offset = 0x00000100
os_version = 9.0.0
os_patch_level = 2021-01
hashtype = sha1
dt = boot.img-dt

Building image...

Using format: AOSP

Appending footer...

Using type: SEAndroid

Done!

last_kmsg:

<5>RAMDISK: Couldn't find valid RAM disk image starting at 0.
<4>VFS: Cannot open root device "(null)" or unknown-block(0,0): error -6
<4>Please append a correct "root=" boot option; here are the available partitions:
<4>0100 8192 ram0 (driver?)
<4>0101 8192 ram1 (driver?)
<4>0102 8192 ram2 (driver?)
<4>0103 8192 ram3 (driver?)
<4>0104 8192 ram4 (driver?)
<4>0105 8192 ram5 (driver?)
<4>0106 8192 ram6 (driver?)
<4>0107 8192 ram7 (driver?)
<4>0108 8192 ram8 (driver?)
<4>0109 8192 ram9 (driver?)
<4>010a 8192 ram10 (driver?)
<4>010b 8192 ram11 (driver?)
<4>010c 8192 ram12 (driver?)
<4>010d 8192 ram13 (driver?)
<4>010e 8192 ram14 (driver?)
<4>010f 8192 ram15 (driver?)
<4>0800 62464000 sda driver: sd
<4> 0801 4096 sda1 52444e41-494f-2044-424f-544130000000
<4> 0802 4096 sda2 52444e41-494f-2044-4e41-000000000000
<4> 0803 20480 sda3 52444e41-494f-2044-4546-530000000000
<4> 0804 8192 sda4 52444e41-494f-2044-5041-52414d000000
<4> 0805 8192 sda5 52444e41-494f-2044-5550-5f504152414d
<4> 0806 8192 sda6 52444e41-494f-2044-424f-544132000000
<4> 0807 40960 sda7 52444e41-494f-2044-424f-4f5400000000
<4> 0808 47104 sda8 52444e41-494f-2044-5245-434f56455259
<4> 0809 8192 sda9 52444e41-494f-2044-424f-544131000000
<4> 080a 43008 sda10 52444e41-494f-2044-5241-44494f000000
<4> 080b 1024 sda11 52444e41-494f-2044-544f-4d4253544f4e
<4> 080c 1024 sda12 52444e41-494f-2044-444e-540000000000
<4> 080d 512 sda13 52444e41-494f-2044-5045-525349535445
<4> 080e 1024 sda14 52444e41-494f-2044-4d49-534300000000
<4> 080f 4096 sda15 52444e41-494f-2044-5354-454144590000
<4> 103:00000 16384 sda16 52444e41-494f-2044-4b45-595245465547
<4> 103:00001 4454400 sda17 52444e41-494f-2044-5359-5354454d0000
<4> 103:00002 512000 sda18 52444e41-494f-2044-4341-434845000000
<4> 103:00003 10240 sda19 52444e41-494f-2044-4849-4444454e0000
<4> 103:00004 51200 sda20 52444e41-494f-2044-4f4d-520000000000
<4> 103:00005 5120 sda21 52444e41-494f-2044-4350-5f4445425547
<4> 103:00006 20480 sda22 52444e41-494f-2044-4e41-445f46570000
<4> 103:00007 1024 sda23 52444e41-494f-2044-4e41-445f52454645
<4> 103:00008 57184256 sda24 52444e41-494f-2044-5553-455244415441
<4>0810 4096 sdb driver: sd
<4>0820 8192 sdc driver: sd
<4>0830 8192 sdd driver: sd
<4> 0831 6144 sdd1 52444e41-494f-2044-4350-454653000000
<0>Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
<0>Kernel loaded at: 0x800ac000, offset from compile-time address 2c000
<0>s3c2410_wdt: watchdog reset is started to 30secs
<3>mif: ss310ap_send_panic_noti_ext: Send CMD_KERNEL_PANIC message to CP
<4>CPU: 3 MPIDR: 80000103 PID: 1 Comm: swapper/0 Not tainted 4.4.111-a2n-g917acc90-dirty #5
<4>Hardware name: Samsung DREAMLTE EUR rev06 board based on EXYNOS8895 (DT)
<4>Call trace:
<4>[<ffffff80080b6cc4>] dump_backtrace+0x0/0x214
<4>[<ffffff80080b6eec>] show_stack+0x14/0x1c
<4>[<ffffff800838bf1c>] dump_stack+0xa0/0xc0
<4>[<ffffff800816e6cc>] panic+0x154/0x294
<4>[<ffffff800952107c>] mount_block_root+0x238/0x2d8
<4>[<ffffff80095212c8>] mount_root+0x6c/0x78
<4>[<ffffff800952142c>] prepare_namespace+0x158/0x1a0
<4>[<ffffff8009520c90>] kernel_init_freeable+0x208/0x224
<4>[<ffffff8008c5d470>] kernel_init+0x10/0x10c
<4>[<ffffff80080b1ba0>] ret_from_fork+0x10/0x30

Any idea what i'm doing wrong ? I didn't install Magisk at all, so just to make sure Magisk doesn't corrupt the boot.img.

EDIT: same result with stock boot.img instead to use my custom kernel.

Now i'll test with old AIK-Linux release.