The topic shouldn’t come up.
I have a male colleague who is gay. I only found because his “partner” needed my help professionally and he ran the situation by me first. The only other time I’ve ever heard him say anything was at a happy hour well away from work.
If he was asked why he didn’t say anything I could see him coming up with some version of it’s no one’s business and has nothing to do with his job performance.
How many of our non-gay co-workers discuss their sex lives at work? Shall we consider their non-discussion as meaning they are "closeted" heteros? It should not be relevant to work.