Thanks!
Did it have the correct resolution in NetBSD 9?
Two things here:
1. This is probably an amdgpu device. Unfortunately, the amdgpu
driver is still experimental and not really ready. You can try it
by loading it in boot.cfg with the line `load=amdgpu', or with the
command `load amdgpu' on one of the `menu=...' lines, but be
prepared for crashes -- I suggest you create two menu lines, one
with amdgpu and one without, so after the one with crashes, you can
boot into the one without and savecore or dmesg to diagnose it.
2. As a stop-gap measure, you can select the EFI graphics output
configuration with the `gop' command at the boot loader. Type
plain `gop' at the bootloader prompt to list the available modes;
type `gop N' to select mode number N in the list.