TX2i, headless on custom carrier card, vulkan not working


We are running a TX2i on our own custom carrier card (and sw tuned to match) (width out any output hdmi/dp) and are having problems getting vulkan based applications, such as ‘vulkan-smoketest’ running.
We are able to get X11, and OpenGL based applications (such as glxGears), to run. (Verified by capturing display :0, using gstreamer, and streaming it to another computer.)
But when running ‘vulkan-smoketest’ it core-dumps.

When running ‘vulkaninfo’ it seems to have no presentable surfaces:
Presentable Surfaces:
GPU id : 0 (NVIDIA Tegra X2 (nvgpu))
Surface type : VK_KHR_xcb_surface
Formats: count = 0
Present Modes: count = 0

(These counts are 2 and 3 when running on a SDK from Nvidia, where vulkan works fine).

When doing a ‘strace vulkaninfo’ on the SDK, I can see that vulkaninfo opens ‘/dev/tegra_dc_0’ and ‘/dev/fb0’.
These devices are not present on the TX2i running on out carrier card.

Does vulkan depends on these two devices, or is there something else that is preventing vulkan from working?

Since we don’t have thecustom board, is it possilbe to reproduce the failure on default board so that we can check and investigate?

Sorry, I’ve poor knowledge about Vulkan on Jetson, but my understanding so far is that it would expect wayland.
Someone more skilled with this may correct me (I’d be happy to learn more).