Comment 152 for bug 1958019

Sorry,
I write to quickly.
So you have to found the line : GRUB_CMDLINE_LINUX_DEFAULT=
Replace or complete with :
GRUB_CMDLINE_LINUX_DEFAULT="mem_sleep_default=deep"

Put GRUB_EARLY_INITRD_LINUX_CUSTOM="/boot/acpi_override"
ERROR in my precedent post juste 1x" not acpi_override"" -> acpi_override", sorry.
This line probably don't exist.

After you have to regenerate grub :
10) Regenerate the GRUB configuration :
sudo update-grub

recheck the step 11, it could, it would be erase by Grub :
> 11) Tell GRUB to load the new DSDT table on boot in its configuration file
> usually located in /boot/grub/grub.cfg. Find the relevant GRUB menu entry
> and add the new image /boot/acpi_override to the initrd lines for the
> images
> that you want the s3 sleep to work in :

sudo nano /boot/grub/grub.cfg
or
sudo gedit /boot/grub/grub.cfg
(it could be easier to find initrd part)
replace in the kernel part initrd in the part menuentry (and all submenu) of the file /boot/grub/grub.cfg :

initrd /boot/initrd.img-5.11.5-051105-generic
> BECOME :
initrd /boot/acpi_override /boot/initrd.img-5.11.5-051105-generic

5.11.5-051105 is for the 5.11.5 kernel, you will have other number, you just have to do it for 5.11 kernels.