1. Who are the other potential love interests in the Empress of Aeser except Markaius? I guess that the female one is Kialee, but who's the other male love interest? If this supposed to be a secret, don't tell!
2. Which characters in the World of Aeser are lgbt+? Tetrine and Tell are bi/pan, Kalavel is attracted to (only?) women, Allie (female mc) and maybe Judy/Felicia are attracted to women... what about other characters?
Kialee is not a romantic interest in Empress, but Kalevel is.
Yeah, I think Kalevel is only attracted to women. I say 'I think' because I don't plan these things. If it feels natural for the character, I go with it. One Tell a Demon ending suggests at least an alliance between Kalevel and a man and maybe something more. However, I can't answer your question about how the other characters are because it may change if it feels right for the character in a different route or context.
I am not very 'commercial minded' in my approach to writing games. I prioritize what seems right within the themes, the characters and what they want, and I aim to be true to the player's choices. So that means I don't prescribe routes like a writer god ("And now! You and you shall smooch at the midpoint whether you like it or not!").
So that means that the answer atm to your other question, is 'probably Julius' because that was what I had envisioned for Empress before I wrote Tell a Demon and introduced Tell as a character. So if Tell and Julius start out with a platonic relationship in Empress, that may mean Julius is a romantic option for Tetrine.
Empress has more of a twisty Noir treatment, esp. later on. So we'll see.