My plan to is to use GitHub not for software sharing but rather to host markdown files on GitHub, those markdown files would be serving tutorial style purposes of documentation's on how to administer arbitrary system such as Linux.
Is is okay to ask such questions on Super User site or where else could I ask this?
Note that this will be about system administration rather than software development.
What you describe in your question sounds like asking how to use GitHub for a particular use- documenting system administration. While system administration is on topic here, writing up how to do it on a website is not (cf the famous- 'boats for programmers' test).
Of course, if you have questions about how local programs on your computer interact with GitHub (eg git or ssh for managing keys), those kinds of questions may well be on topic here.
Their github tag reads:
Hosting service for software projects using the Git revision control system. For questions about using GitHub web interface such as: how to use its search, pushing your branch or repository, wiki page formatting and directories, and syntax highlighting on README files.
It sounds like this might cover your use case.
Github as a Web service is probably off topic here unless your specific problem with it in in using the git software on your computer to push to it.
Problems specific to Github itself might fit better at Web Applications. But only insofar as it would be about the web interface.
Our help center uses the phrase "except insofar as they interface with your computer" and while it mentions random electronics the same applies to website and apps. If the problem is specifically in your browser or local tools then it is on topic here. If it is a problem with the website itself then it belongs on Web Applications
Questions about what kind of structure you should use for your documentation would probably be off topic in both places as it is highly dependent on your task and is largely opinion based.
