BTRFS ran out of space during update, now I can't boot, GRUB does not find kernel

Thank you for the directions!

I’ve booted Manjaro GNOME from a USB flash drive with Ventoy.

I’ve successfully chrooted into my BTRFS partition following the instructions of your how-to, with just a few changes:

$ sudo su -
# lsblk --fs
# mount -t btrfs -o subvol=@ /dev/sda8 /mnt
# btrfs subvolume list /mnt
# mount -t btrfs -o subvol=@cache /dev/sda8 /mnt/var/cache
# mount -t btrfs -o subvol=@log /dev/sda8 /mnt/var/log
# mount -t vfat  /dev/sda1 /mnt/boot/efi
# mount --bind /dev /mnt/dev
# mount -t proc proc /mnt/proc
# mount -t sysfs sysfs /mnt/sys
# mount -t efivarfs efivarfs /mnt/sys/firmware/efi/efivars
# chroot /mnt /bin/bash
# echo 'nameserver 8.8.8.8' > /etc/resolv.conf

First I tried:

# paccache -rvk0

bash: paccache: command not found

# pacman -S pacman-contrib

resolving dependencies...
looking for conflicting packages...

Packages (1) pacman-contrib-1.10.6-1

Total Download Size:   0.05 MiB
Total Installed Size:  0.12 MiB

:: Proceed with installation? [Y/n] 
error: Partition /var/cache too full: 5133 blocks needed, 1503 blocks free
error: failed to commit transaction (not enough free disk space)
Errors occurred, no packages were upgraded.

Then I tried following your how-to:

# [ -f /var/lib/pacman/db.lck ] && rm -f /var/lib/pacman/db.lck
# pacman-mirrors -f && pacman -Syyu

::INFO Downloading mirrors from Manjaro
::INFO => Mirror pool: https://repo.manjaro.org/mirrors.json
::INFO => Mirror status: https://repo.manjaro.org/status.json
::INFO Using default mirror file
::INFO Querying mirrors - This may take some time
  1.720 United_States  : https://ohioix.mm.fcix.net/manjaro/
  0.173 Brazil         : https://manjaro.c3sl.ufpr.br/

...

resolving dependencies...
looking for conflicting packages...

Packages (5) chromium-127.0.6533.119-1  gnome-shell-extension-dash-to-dock-93-1  wine-9.14-1  xapp-2.8.5-1  xfsprogs-6.9.0-1

Total Download Size:   101.09 MiB
Total Installed Size:  923.89 MiB
Net Upgrade Size:       -0.07 MiB

:: Proceed with installation? [Y/n] 
error: Partition /var/cache too full: 31001 blocks needed, 1503 blocks free
error: failed to commit transaction (not enough free disk space)
Errors occurred, no packages were upgraded.

My disk is really full…

Do you have any ideas on what should I try next?