Your comment led me down a bit of a rabbit hole and I found this on Wikipedia:

When writing in languages such as Danish and Norwegian, where the empty set character may be confused with the alphabetic letter Ø (as when using the symbol in linguistics), the Unicode character U+29B0 ⦰ REVERSED EMPTY SET may be used instead.

It also mentions what you are alluding to:

In the past, "0" (the numeral zero) was occasionally used as a symbol for the empty set, but this is now considered to be an improper use of notation.

And, as a programmer, don't get me started on nulls...or undefined...or truthyness.