There are no requirements regarding gender identities to publish, but it is an unspoken expectation among the COG/HG audience (not the company) that a game has options for everyone. We’re a very inclusive forum and I’ve seen games without LGBTQ+ gender/sexuality options or romance options get panned by the audience for not having them. I personally don’t play any games that force me to play as a heterosexual character or insinuate in any way that my character is heterosexual. Many players here hold the same philosophy.
All that is to say that no one will force you to write LGBTQ+ characters/options, but a lot of the audience may not take interest in your game if you don’t. It’s up to you decide if that trade-off is worth it.