Start with one mixed line
When your ship brings back more resources than your station has dedicated dock outputs, run a mixed belt to a sorting point or add another dock. In an October demo Steam discussion on unloading several resources, players reported using an unrestricted output and sorting the items downstream. They also suggested another dock or manual transfer when that was simpler.
Sort cargo after it leaves the dock
Leave one output unrestricted if your dock supports that configuration. Run the belt to a splitter or balancer, then branch toward the consumers or storage for each resource. Test the route with small amounts of each item and follow the belt past the sorting point. The test succeeds when all the expected items reach a usable destination.
For a load of ice, titanium, and nickel, you could give ice its own output and sort the two ores on the other line. Start with the destinations connected so an unwanted material has somewhere to go.
Choose a separate dock when the flows need independence
A dedicated output is easier to inspect because only one resource should appear on it. If two processing lines already need their own steady supply and mixed sorting complicates them, an additional dock can give the third resource a separate path. For one leftover shipment, move it manually and save the build space for a route you expect to use again.
FAQ
Does the port limit cap the number of resources I can unload?
The October players distinguished the number of physical ports from the number of items a mixed belt can carry. Verify the behavior on your build before rearranging the station.
Where do I put the sorting equipment?
Place it after the dock and before the first machine that accepts only one of the incoming resources.
What should I check if one resource never arrives?
Check that it is actually in ship cargo, then inspect the port's item filter and the branch leading to that resource's destination.