Where is the discourse.conf file?

Further to that, I assume if I can do that (install nano and edit .conf) then I should expect during any upgrade it will be overwritten?

I see mention the possible use of replace commands in app.yml file NGinx.conf File location to compensate this but I suspect maybe I am comprehending things incorrectly and that is a very old topic where the link to the examples are not working. So may be irrelevant.