Hello world !
It’s the first time i post some text about LFS and give my apologies if i make
some formals mistakes according the communication rules.
First, i am sorry for my english, i am french and able to read existing english
text, but almost null to write something.
Thank to everybody who takes time to read me.

Following strictly LFS manual (release 7.10 and now 8.2), I found all that i
need and I got success on a VM under VirtualBox running on a MacbookPro.
Later I complete it with BLFS and obtain a nice result with the tools that I
hoped.
All along that installation, I kept all the used scripts (one for each step)
and replay them under the same conditions on my MAC. Since a long month i still
blocked for making a good kernel. Kernel compilation seem OK, Grub-2
configuration is good BUT at starting fail.

1-Operating Context :
Computer used : MacBookPro11,3
Intel Core i7 - 2,3 Ghz
Processor : 1 / Cores : 4
Memory : 16 Go
Host system : Archlinux (iso 2018.03.01-x86_64) on a SD card
kernel archlinux 4.15.6.1 : grub-2 - systemd - Xorg - network

Guest system : LFS 8.2 on an external SSD Lacie sharing as :
sda1 for /boot ext2
sda2 for swap swap
sda3 /sources ext4
sda4 / ext4
kernel 4.15.3 - grub-2 - init with systemd
The SSD is plug on a Thunderbolt port/
Result : The starting seem complete, the login prompt showing then nothing
append, the keyboard is down the last line is
< machine login: [ 2.255104] clocksource: Switched to clocksource tsc >
Tries done :
1 - booting with < clocksource=hpet > inside grub.cfg ==> the last line
(clock source ...) disappears BUT the keyboard don’t answer.
2 - booting with single user <S> dans le grub.cfg ) ==> on more time, no
active keyboard even to type <ctrl-d>
3 - copy kernel 4.15.6.1 & his associate sysramfs both compiled on ArchLinux
host on /boot of Guest LFS (to be sure I unplugged SD card)
==> then start successful, to be sure once more i check some files : the
started system is LFS.
4 - compile 4.15.6 kernel with .config file as is the first time
==> kernel panic (perhaps because ArchLinux don’t provide a System.map and
no modules are loaded)
5 - compare config files Archlinux & LFS to make some changes
==> kernel panic
6 - add intel-code on initrd line of Grub-2 ==> kernel panic
7 - Finally as system may start with files kernel from the host ArchLinux :
I redo it and get access to log using the <journalctl> command.
Then i became able to compare the results from both "LFS alone" and
"ArchLinux on LFS" starts boots.
I found the most signifiant among else at the beginning of the log :
In LFS :
...
20:24 kernel: tsc: Fast TSC calibration failed
20:24 kernel: tsc: Unable to calibrate against PIT
20:24 kernel: tsc: No reference (HPET/PMTIMER) available
20:24 kernel: Zone ranges:
20:24 kernel: DMA [mem 0x0000000000001000-0x0000000000ffffff]
20:24 kernel: DMA32 [mem 0x0000000001000000-0x00000000ffffffff]
20:24 kernel: Normal [mem 0x0000000100000000-0x000000047f5fffff]
...
In ArchLinux :
...
21:52 kernel: tsc: Fast TSC calibration using PIT
21:52 kernel: Zone ranges:
21:52 kernel: DMA [mem 0x0000000000001000-0x0000000000ffffff]
21:52 kernel: DMA32 [mem 0x0000000001000000-0x00000000ffffffff]
21:52 kernel: Normal [mem 0x0000000100000000-0x000000047f5fffff]
...
My conclusions :
Init step is fully done.
Keyboard still mute.
May be Clocksource and/or Watchdog are in question ?
Of course my Kernel .config file is wrong according to the MAC computer.
Questions:
Does somebody as already compile a Linux Kernel on a Macbook as mine and
successfully start it ?
Where to fetch around the Kernel, his modules and the starting line inside
Grub-2 ?
I may post the used .config file and the logs of starting both LFS and
ArchLinux issued of <journalctl> command.
And more of course if one need it.

I don't think it is clocksource issue. As you mentioned, this is input device issue. I think you misses your device driver.

You can build kernel and install modules from the same kernel source with the same .config under chroot, instead of copying.

For journalctl, you can search `input :` to see your kernel can find your keyboard.

While in the chroot and building the kernel try this.

make localyesconfig