javacpp ships DNNL with the GPU engine disabled. This is the default build in upstream DNNL:

GPU Engine
Intel Processor Graphics and Xe architecture-based Graphics are supported by the oneDNN GPU engine. The GPU engine is > disabled in the default build configuration. The following additional requirements apply when GPU engine is enabled:

OpenCL* runtime library (OpenCL version 1.2 or later)
OpenCL driver (with kernel language support for OpenCL C 2.0 or later) with Intel subgroups extension support

What is required to enable it in javacpp (by default)? Does the absence of javacpp preset for OpenCL block it, or it it not required, but you simply chose to follow the DNNL default?