TLDR
create a new sdcard - using a patched installer - and arm-unstable branch
sudo pacman -Syu base-devel git --needed
git clone https://gitlab.manjaro.org/manjaro-arm/applications/manjaro-arm-installer.git
cd manjaro-arm-installer
curl -O https://gitlab.manjaro.org/manjaro-arm/applications/manjaro-arm-installer/uploads/9b8a1538979012a883e230c2eba6b500/01_set_branch.patch
patch -u manjaro-arm-installer -i 01_set_branch.patch
sudo systemctl restart systemd-binfmt
sudo bash manjaro-arm-installer arm-unstable
Place the sdcard in your pi and boot it
- USERNAME is the username you used above
- replace fido below with the one you used
USERNAME=fido
userdel -rf $USERNAME
sudo pacman -Syu git
git clone https://github.com/fhdk/lxqt-kwin.git
cd lxqt-kwin
bash setup.sh $USERNAME
cat << EOF > /etc/X11/xorg.conf.d/99-v3d.conf
Section "OutputClass"
Identifier "vc4"
MatchDriver "vc4"
Driver "modesetting"
Option "PrimaryGPU" "true"
EndSection
EOF
Reboot the system