On my forum, I (and occasionally other users now that I think about it) have sometimes used “Discourse” on some posts without thinking about it, but users with little knowledge of IT stuff could be a bit puzzled, so we (my community and I) usually refer to it at “the forum”.
The forum itself, though we moved to Discourse in 2017, is old: created in 2004, and has always been known by the community as “the forum”.
Funny stuff to think about it though… “Forums” are sometimes considered as something from the ancient Internet era by youth who are massively using social networks (and, obviously, Facebook groups…).
And some modern forum engines won’t use “forum” as their community platform subdomain. Examples:
https://meta.discourse.org/
https://community.nodebb.org/
https://discuss.flarum.org/
