Before a Google search just now, I had never heard of SMF before.
Oh my.... it's like IPB & vB without the $$ 😉 SMF is lagging behind in some aspects like Paid subscriptions and other "addons" that vB and IPB come with, but it's right up there next to it.
If you're reading this thread wondering about forums, I'd suggest you skooch on over to Forum Matrix and do a broad comparison on a few different BB types.
Right now, it shows SMF as only doing mySQL. While that's true, they are currently doing testing of their abstraction layer for Postgre, MySQLi and maybe MSSQL (not sure about that one). Lots of the blank areas are filled by mods from members. Each mod is obviously tested and approved before it's downloadable from their site. But it's an interesting comparison. SMF is also the only board to use WAP 😉