When reading the Egyptian myths I was struck by their similarity to Greek myths.
This lead me to wonder whether any non human creature (so no ghosts, giants or dwarfs) appears universally or nearly universally across many cultures myths.
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It has long been a popular fantasy among amateur students of myth that all peoples share the same stories. This is clearly an example of wishful thinking.
Folklorists have developed these tools called Motif Indexes. I'm not quite sure what you mean by "non human creature", but creatures like phoenix have entries in the index. A motif index would then list every culture that contains a myth/story about phoenix. The key here is that there isn't a single example that we can point to where the motif is universal, i.e. it is present in the stories of every culture known to mankind.
So no, there isn't an example of a "non human creature" that "appears universally or nearly universally across many cultures myths."
If you're interested in the similarities and differences between the stories of different cultures, then I would recommend that you learn more about motif indexes.
All major religions today are byproducts of the Mysteries of Eleusis, which is why they all smell alike. The prehistoric hunter gatherer calendar was based on either of two systems: the constellations of the ecliptic plane or the constellations of the galactic plane. The creatures represented in either culture's pantheon come from those astrological origins. For many years the Axial Period was thought to be the turning point when these cultures blended but recently the process appears to be more erratic and the merging process more complicated. The Index of Deities and Demons describes the earliest known ecliptic system from Upper Paleo France (Chauvet and Lascaux). Judith Dillon's FUTHARK RUNES MYSTERY TRADITIONS 2 describes the Celtic galactic system and its roots well. Macbain's Celtic Mythology and Religion describes a blended system.