@jana @MagicLike The irony is that initial versions of the T480 port didn't work properly with coreboot's native Intel graphics code either. It was quickly fixed; so quickly that I reverted the above patch adding Intel's VGA ROM, like within 1 hour.
Anyway, if you're using SeaBIOS, you just insert that Nvidia ROM properly into CBFS.
It probably won't work on FreeBSD - and I don't remember if it was tested under Linux with Nvidia's binary driver. Perhaps @mkukri can tell you more, he tested it.