VK_EXT_external_memory_dma_buf not showing up

Supposedly 515.48.07 added support for this extension, and on my laptop I can see it in vulkaninfo, but on a server running 515.65.01 it’s not appearing. I’ve checked that nvidia-drm is loaded with modeset=1 (and checked the parameter value in /sys/modules). I’ve tried using the Ubuntu packages and the .run file, I’ve tried using the open-source and non-open-source kernel modules, and I’ve tried installing that latest Vulkan SDK. The server is running Ubuntu 20.04 with kernel 5.13.0-27-generic.

Is there anything else I should try to get this extension to appear, or any way to debug why it doesn’t?