Best way to cover external XPS insulation
For covering exposed XPS, especially on foundations (though not limited to there) "Parging" (pretty much a layer of a stucco-like product) is fairly normal; you can get stuff marketed for exactly this job, or not, as you prefer. In the typical thin application, it provides sun/UV protection and appearance similar to concrete, with a minimal level of impact resistance.

In a more abusive location a full stucco coat with reinforcement may be needed.