After searching for an answer to my problem, I decided to ask on SF, because there are many other docker related questions here. Here is my question:
Also, this SF meta question seems to confirm that docker questions are welcome on SF:
Yet, my question was promptly closed as off-topic. I asked what made it off-topic in a comment, but got no reply after a day, so I am asking here.
I am not asking for the question to be re-opened, as I managed to solve the problem myself eventually, but I am still unclear as why it was closed, and since I expect to have more docker-related questions in the near future, I'd like to be told why it doesn't belong on SF, and how am I meant to decide if my future docker questions should be posted on SF, or stack-overflow, or super-user?
While I was physically "at home" when I asked the question, my setup is exactly the same as my office PC (and mostly dictated "management rules", which leave me little choice), so it falls under "managing information technology systems in a business environment" IMHO. I would have been sitting at work to do this, if I wasn't so overwork, that I have to "learn stuff" at home... OTOH, maybe the question was closed because it should go on SO instead (rather than because it's "home user"); I cannot tell, without an explanation.