HA OS installation - unable to run python scripts from shell

Hi there,
I am trying to monitor an old Samsung AC, following the guide:

I am stuck at the point in which I am asked to run a Python script.
Loggin from SSH with Putty I have this answer:

[core-ssh ssl]$ python3 server.py
-bash: python3: command not found

I searched the community, but I could not find an answer on how to install/run Python.

I installed the HA operating system, running in an old laptop. Everything is fine but I would like to control this old AC by means of Wifi.

Here I posted my question a few days ago:

I will appreciate any advice on that topic.

thanks