If using the third pronoun is considered supporting something haram (like homosexuality) then it would be haram and yes you’d have to search for another job. But if in your society it’s not considered as supporting a sinful lifestyle like homosexuality, then using the “they” pronoun would be ok.
You can also be creative and just avoid using pronouns altogether. Instead of saying “he” came or “she came” or “they” came you can say “this person came.”