gender - How to explicitly specify non-binary support when using pronouns?

My native language uses the equivalent of he/his as the default gender-less pronoun. When using English (as a second language) most people use "he/she" or "him/her" to indicate a person of unknown/unspecified gender. E.g.:

He/she must join the team by the end of this year.

I am aware that singular they does the trick, but I am interested in a form that explicitly acknowledge non-binary genders. Something like “he/she/*”, where * allows for anything else.

Question: How to explicitly specify non-binary support when using pronouns?

Answer

Any non-binary person I've known is happy with the usage of singular "they" which you mention. This is inclusive of non-binary people. It is admittedly not a list of alternatives with one specifically for non-binary people, but that is OK.