I also tried this accelerator profile

openstack accelerator device profile create L40S_GPU '
[
  {
    "trait:CUSTOM_NVIDIA_26B9": "required" 
  }
]'

But when using openstack flavor create --public --vcpus 8 --ram 16384 --property accel:device_profile=L40S_GPU 16gb.8cpu.vol.gpu

And then creating a VM I got nova.exception.NoValidHost: No valid host was found.