Redirect rules for SMF 2.0.
Option 1 - .htaccess
There are a few things for .htaccess to work correctly:
SMF 2.0 was using normal URLs, like "https://www.domain.com/smf/index.php?board=5.0"
"Use full friendly URLs" in Xenforo is enabled
During the import to Xenforo, you choose to retain ID's...