For anyone who needs 470 series of legacy nvidia-driver on #FreeBSD:
Now there's a review D49457 for upgrading ports to 470.256.02.
https://reviews.freebsd.org/D49457

It also contains patch for x11/linux-nvidia-libs-470 to keep them in sync.

Without this patch, 470.256.02 does not build.

Although I've opened the review as per request in Bug 285069,
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=285069
unfortunately I myself don't using 470 series of drivers. But it is reported to work with default options in Bug 285069.