- Boot into Linux
- Upgrade the kernel on Debian as root execute:

mkdir -p /boot/efi/m1n1
dpkg -l | grep linux-image | awk '{print $2}' | xargs apt-get remove -y

cat <<'EOF' | sudo tee /etc/X11/xorg.conf.d/30-modeset.conf
Section "OutputClass"
    Identifier "appledrm"
    MatchDriver "apple"
    Driver "modesetting"
    Option "PrimaryGPU" "true"
EndSection
EOF

echo 'deb https://thomas.glanzmann.de/asahi testing main' | sudo tee /etc/apt/sources.list.d/glanzmann.list
sudo curl -sL -o /etc/apt/trusted.gpg.d/thomas-glanzmann.gpg https://tg.st/u/thomas-glanzmann.gpg

sudo apt update
sudo apt install -y m1n1 linux-image-asahi libgl1-mesa-dri
sudo apt upgrade -y

- cd /boot/efi; tar cfz /root/efi.tar.gz EFI/
- edit /etc/fstab # and comment out the mount point for /boot/efi
- Transfer the /root/efi.tar.gz on a webserver or msdos usb stick
- umount /boot/efi
- parted /dev/nvme0n1 print
- parted /dev/nvme0n1 rm <partition number of your esp>
# stub is the 2.5GB partition
- parted /dev/nvme0n1 rm <stub>
- halt -p
- Boot into 1tr by keeping the power button pressed and select 'Options'
- Run the asahi installer:

        curl -sL https://alx.sh | sh

- Select 'm1n1 + UEFI' and follow the installation along. If you have not
  enough space, reclaim space from macos in order to finish the installation.

- Once the instllation is finished, put back the content of the tar archive
  under 1tr or macos:

        diskutil list
        mkdir /Volumes/efi
        mount -t msdos /dev/<identifier of esp partition> /Volumes/efi
        cd /Volumes/efi
        tar xf path/to/efi.tar.gz
        umount /Volumes/efi

- edit /etc/fstab # put the /boot/efi mount point back. Id can be found out with blkid
# If you need help or don't succeed email me at thomas@glanzmann.de
# I'll make a video of this procedure shortly