Rotor sails (large cylindrical sails that use the Magnus effect) have been deployed by Maersk and have been proven to result in fuel savings [0]. Years ago I believe Maersk also ran a test project where they deployed traditional sails on ships.
Experimental wind-assist sails of various sorts for modern cargo ships have been around at least a decade, and the question has generally been whether the fuel savings is worth the added capital and operational expenses of maintaining the sails. My understanding was that it isn't yet clear that this is the case, which is why they aren't deployed everywhere.
The first article I can remember reading about kites on cargo ships was in the Economist in 2005. These things have been around for a long time and have completely failed to have a meaningful impact.
[0] https://maersktankers.com/newsroom/norsepower-rotor-sails-co...