Converters exist to migrate SMF to phpBB, etc. Though I don't know that SMF is the problem so much as the ancient version we're using. I don't know what hitches the version upgrade had, though.
I'm a developer not an ops guy, but given file/DB read access I'd be willing to put some time into doing a test-run on an AWS EC2 server of upgrading the SMF version, and/or migrating to alternate forum software. If successful at one or both, we could decide where to go from there with the actual site.