Build x86_64 linux kernel on ubuntu how to:
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Get the latest kernel at: https://www.kernel.org/
Can download kernel using wget for cli access.

tar -xvf linux*xz

sudo apt-get install git fakeroot build-essential ncurses-dev xz-utils libssl-dev bc flex libelf-dev bison

cd linux-X.X.X

*Get your all ready configured kernel setting (from previous made or official Ubuntu by):
cp -v /boot/config-$(uname -r) .config


make menuconfig

*For ubuntu you must remove keys (requires secure boot in UEFI to be disabled after):

scripts/config --disable SYSTEM_TRUSTED_KEYS
scripts/config --disable SYSTEM_REVOCATION_KEYS

*On Ubuntu 23.10, you may need these packaged installed in order to compile:
sudo apt install libelf-dev

Mow build:
make -j$(nproc) -o2

Then install moduals:
sudo make modules_install


Strip unnessacary data from moduals to help prevent "out of memory" right on boot of new kernel:
sudo su
cd /lib/modules/<new_kernel>
find . -name *.ko -exec strip --strip-unneeded {} +
exit

sudo make install

sources (OG):
https://phoenixnap.com/kb/build-linux-kernel
https://forum.manjaro.org/t/cannot-switch-kernel-errors-out-of-memory-and-you-need-to-load-the-kernel-first/62575/13
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1842320
https://unix.stackexchange.com/questions/120198/how-to-fix-boot-into-initramfs-prompt-and-mount-cant-read-etc-fstab-no-su
https://unix.stackexchange.com/questions/270390/how-to-reduce-the-size-of-the-initrd-when-compiling-your-kernel

Date (OG): December 6th 2022.

Sources (Update 1):
https://github.com/sslab-gatech/opensgx/issues/20

Date (Update 1): October 3rd 2023.