It’s not clear what you are asking because var arr = [[1,2,3],[4,5,6]];
is an array having two elements, each of which is an array having three elements, each of those is an Int. And your sort example sorts the two-element array, by the value of their first elements.

It is not the same as var bytes = Bytes(6);
which is an array having six elements, each of which is a Byte.

The typical sort for a Byte array would be sort(bytes, (a,b)->a-b);. If you need to normalize the result values to (-1,0,1), then sort(bytes, (a,b)->a == b ? 0 : a > b ? 1 : -1);

Is that what you are asking?

If you want to treat the elements of the Byte array as discrete sets of three elements, then you will have to implement a custom sort routine, because a normal sort on an array will sort all elements, NOT sets of elements.