Multipass cloud-init file for making a Qt6.4.2 dev system on Ubuntu 23.10 (mantic) First comment is how to make the multipath call.

gistfile1.txt

#multipass -vv launch --name default --cloud-init ubuntu23ci.txt -c 2 -m 4G mantic --bridged --timeout 500
# When cloud-init is used to make a custom image, it is accomplished as the root user, so if 
# permissions or ownership of files is important later, it should be adjusted as required here.
users:
  - default
package_update: true
package_upgrade: true
packages: 
  - cmake
  - nano
  - net-tools
  - build-essential
  - qt6-base-dev
  - qt6-base-private-dev
  - libqt6websockets6-dev
  - libqt6serialport6-dev
# run commands
# default: none
runcmd:
  - mkdir /home/ubuntu/src
  - cd /home/ubuntu/src
  - git clone https://github.com/qt/qtmqtt -b 6.4.2
  - cd qtmqtt
  - mkdir build
  - cd build
  - cmake ..
  - make -j3
  - make install