At the moment there are ligatures for != and !==. However, for example in Mathematica the function UnsameQ is represented by =!=. The symbol actually shows up currently as =≠which is not particularly pretty.
This is also widely used in Scala DSLs, because !== and =!= have different operator precedence.
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This is also widely used in Scala DSLs, because !== and =!= have different operator precedence.