Nethogs is a tool that allows you to see what PID's are using the most bandwidth and is normally installed on GNU/Linux systems by default, apparently, it is not included in pureOS I believe this to be a mistake.
The tool nethogs is available in PureOS in the package nethogs. I.e. the tool is "included in most Linux distributions" as was quoted in that forum thread you are linking to.
What makes you rephrase here to instead state that it is "normally installed [...] by default"?