[Samsung Galaxy Tab S6 Guides, News, & Discussion] fonix232:
{Mod edit: Quoted post has been deleted. Oswald Boelcke, Senior Moderator}

Ah, so it's annoying to ask for precise instructions when you're practically winging it here with half-assed "it's available elsewhere" and "it's obvious" statements. I repeat, because apparently you're hard of reading, IT IS NOT OBVIOUS.

First of all, as you'll see, you've edited your comment without any notice. This edit is not reflected in my reply, so the CI grid link still points to the original one you listed, the 4.19 stable: https://ci.android.com/builds/branches/aosp_kernel-common-android-4.19-stable/grid?legacy=1

This branch has absolutely no boot.img's.

Since you edited it to point to the mainline kernel: https://ci.android.com/builds/branches/aosp_kernel-common-android-mainline/grid?legacy=1

my comments about no boot.img's obviously doesn't apply anymore. However, the part where multiple targets still have boot.img's, does. As even on the mainline branch, there's about 30% of targets that contain a boot.img, and half of those are aarch64.

But let's just put that aside for a moment and presume the first three points of my above questions are answered.

I've tried a number of those boot.img's, extracted using the official mkbootimg from Google, even tried using the mkbootimg hosted by the Ubuntu repos, the result is the same: a non-booting boot.img.

Here's what I've done:

Used `unpack_bootimg` to extract stock boot.img (after unpacking from boot.img.lz4)

user@ubuntu:/[..]/Samsung/boot$ unpack_bootimg --boot_img boot.stock.img --out stockboot_magic: ANDROID!
kernel_size: 49839901
kernel load address: 0x8000
ramdisk size: 0
ramdisk load address: 0x0
second bootloader size: 0
second bootloader load address: 0x0
kernel tags load address: 0x1e00000
page size: 4096
os version: 12.0.0
os patch level: 2023-08
boot image header version: 1
product name: SRPSC20B006
command line args: console=null androidboot.hardware=qcom androidboot.console=ttyMSM0 androidboot.memcg=1 lpm_levels.sleep_disabled=1 video=vfb:640x400,bpp=32,memsize=3072000 msm_rtb.filter=0x237 service_locator.enable=1 swiotlb=2048 androidboot.usbcontroller=a600000.dwc3 firmware_class.path=/vendor/firmware_mnt/image loop.max_part=7
additional command line args:
recovery dtbo size: 0
recovery dtbo offset: 0x0
boot header size: 1648

Used `unpack_bootimg` to extract mainline boot.img:

user@ubuntu:/[..]/Samsung/boot$ unpack_bootimg --boot_img boot.mainline.img --out mainline
boot_magic: ANDROID!
kernel_size: 33286656
ramdisk size: 0
os version: 0.0.0
os patch level: 2000-00
boot image header version: 4
command line args:

Ran `mkbootimg` with the parameters of the first output, but using the KERNEL file from the second output:

user@ubuntu:/[..]/Samsung/boot$ mkbootimg \
--kernel mainline/kernel \
--ramdisk stock/ramdisk \
--kernel_offset 0x8000 \
--tags_offset 0x1e00000 \
--pagesize 4096 \
--os_version "12.0.0" \
--os_patch_level "2023-08" \
--header_version 1 \
--board SRPSC20B006 \
--cmdline "console=null androidboot.hardware=qcom androidboot.console=ttyMSM0 androidboot.memcg=1 lpm_levels.sleep_disabled=1 video=vfb:640x400,bpp=32,memsize=3072000 msm_rtb.filter=0x237 service_locator.enable=1 swiotlb=2048 androidboot.usbcontroller=a600000.dwc3 firmware_class.path=/vendor/firmware_mnt/image loop.max_part=7" \
--out boot.repacked.img

Yet, the output boot.img won't boot at all. In fact the resulting boot.img is half the size of the previous (both mainline and stock were 64MB, the repack is 32MB), and there's some more inconsistencies in the header as well.

Buddy I was building custom ROMs when you didn't even know what Android is. I suggest you take back from the attitude, especially when incredibly clear (and hardly nonsensical) questions are being asked, especially when you half-ass every single "guide" you write.