I've followed the instructions, and when running the install_prereq.sh , but once it has finished installing the apt-get packages, it has an error as below.

error: externally-managed-environment

× This environment is externally managed
╰─> To install Python packages system-wide, try apt install
    python3-xyz, where xyz is the package you are trying to
    install.

I've copied the line out of the .sh file, and edited it from

sudo python3 -m pip install --user --upgrade paho-mqtt tornado git+https://github.com/drbild/sslpsk.git pycryptodomex

to

python3 -m pip install --break-system-packages --user --upgrade paho-mqtt tornado git+https://github.com/drbild/sslpsk.git pycryptodomex

(i.e. removed sudo and added --break-system-packages)

This seems to install all of the Python packages correctly, but can the developers confirm that this is correct please??