Domain = 6

You don't need to free this memory, because Unity frees it automatically at domain unload. However, to conserve memory, you can free it at any time. Freeing a large number of such allocations in one frame, such that the array of freed pointers is larger than L2 cache, might exhibit a measurable loss of performance.

Note: The Domain allocator can track a maximum of 262144 (256 * 1024) individual allocations. If the number of allocations exceeds that number, Unity logs an error and does not free excessive allocations automatically.