Is it possible to configure Discourse in a way that makes it look more like old-style PHPBB like boards where the “homepage” is a list of categories, and not the more fire hose style list of topics it is by default?
Yes select the categories view in the setup wizard that runs after you install.
Go to admin, site settings. Search for “top_menu”. Move “Categories” so it’s the first item in the list. (see below)
There’s also the “desktop category page style” which you may want to look into
Edit: @codinghorror beat me
Remember the wizard is safe to run at any time. I wouldn’t tell people to do it that manual way any more.
Maybe there should be a link to the wizard on the admin page.