I adore Vorkosigan series; I read it at least half a dozen times. There are a few queer characters throughout the series: Aral (main character in the first two books, ordered chronologically, and a side character in a bunch more by the virtue of being the main character’s father) is bisexual, Bel is a hermaphrodite (genetically engineered race). Bujold also retconned a polyam relationship that includes Aral and Cordelia (and Jole is also bisexual). It’s such a good idea—I can see it for them—but I hate the execution. There’s probably more, but mostly as less significant side characters.

I’m not sure that I could say that enjoy single-gender planet trope based on one story, but it’s true that Ammonite has been on my TBR list for a while.