If for lesbian fiction, you will accept a canon lesbian relationship but in a novel not centred on romance, I would recommend Seth Dickinson's The Traitor (Baru Cormorant). It's about a woman whose home is taken over by an empire and who grows up to join the ranks of the empire to try and take it down from within. The first book ends unhappily for the love interest; a second book is to come out later this year.