I recall an episode of Jerry Springer where a man was admitting to his girlfriend that he’d been cheating. It was with a man but he was being intentionally vague waiting for the big shock for the audience. He refer to him as “they” and his girlfriend said “They? How many of them are there?”.

There are terms that can be used, but they seem forced when gender specific ones are so common that it hints at something and in this case would similarly spoil the reveal.