Stymied by the kernel being in a different place than other ports.
#RTFM
"with different boot loader schemes ...
netbsd-GENERIC: A normal kernel in ELF format.
netbsd-GENERIC.img: In NetBSD >= 9, formatted for the RPI bootloader.
netbsd-GENERIC.bin:
In NetBSD >= 9, ??????
In NetBSD 9, this kernel WILL NOT boot.
netbsd-GENERIC.ub: A kernel in uboot format.
...
copy this either to /boot/kernel.img (First generation Pi, Pi Zero hardware) or to /boot/kernel7.img (Pi 2, Pi 3 hardware)
..."