This is something very important to us as well.
When I Generate a Call list for a region my sales rep is going to be visiting the following week I need to se the closest Zip codes so my CS can try to arrange a Schedule. Right now I am making a second field (ZIP_CODE_sort) and enterring as number, so i can filter by range.
But Filtering with "starts with " is basic stuff, Hubspot should have it by now