When making halloumi, you can very easily make ricotta from the same pot of milk; and with no extra time involved as the halloumi drains while you make the ricotta.
You can also use cow’s milk with this recipe guide.
4 litres of milk is a great amount to get used to a recipe without wasting precious milk if it goes terribly wrong (and even then, you can probably still salvage it in one form or another), as well as producing a reasonable amount of cheese for the effort of making it.