As long as it is milkweed, monarchs will use it as a host plant. Referring to milkweed as "ornamental" is more of a marketing strategy to convince people to buy a particular variety of milkweed because of its attractive flowers. For example, swamp milkweed is sold as "ornamental milkweed," and it is a native milkweed in many areas of the United States, including Illinois where I live.

In the prairie areas, common milkweed is by far more prevalent. I have both common milkweed and swamp milkweed. Although I find the vast majority of eggs/caterpillars on the common MW, monarchs do use both.

@MikeEC
"Ornamental Milkweed" is also synonymous with Tropical Milkweed, which should be avoided, especially up North