transgender symbol
Yes it’s the end of 2019 and i (ben) had to look this up.
The Transgender Symbol
Another transgender symbol, a combination of the male and female sign with a third, combined arm representing non-binary transgender people (Unicode: U+26A7 ⚧).
From https://www.symbols.com/symbol/the-transgender-symbol
This was the first source that explained that the extra left arm is of course a sort of combined male and female arm to represent nonbinary.
Unicode just confusingly calls this: “Male with Stroke and Male and Female Sign”