Accelerate is a bit different in being both overall more high level API and specific to Apple (and abstracts away the usage of AMX and ANE too). On the other hand, Vector<T>/Vector128/256/512<T> in .NET is what is 'portable-simd' to Rust except it is not in preview and widely used across standard library where applicable.
As of now, Vector<T> automatically targets AVX2, SSE4.2 and AdvSimd (NEON). Vector256<T> targets AVX2 (for the lack of ARM counterpart) and Vector128<T> targets SSE / AdvSimd respectively.