I keep a goodreads list of No Romance Books for exactly this reason lol.
The Murderbot Diaries by Martha Wells. Sci-fi series, space opera-ish. You've got a lot of recs for this already.
Ancillary Justice by Ann Leckie. Sci-fi space opera. I've only read the first one still but it's brilliant.
Piranesi by Sunanna Clarke. Fantasy. A man lives alone in an infinite House over an equally infinite ocean. Ethereal and luminous and melancholy and beautiful.
Jurassic Park by Michael Crichton. Sci-fi thriller. Cloning! Dinosaurs! Math! I still love it.
The Jewels of Aptor by Samuel Delaney. Weird 1960s science-fantasy. The main characters could be read as romantic if you want - the homoeroticism can't be unintentional - but there isn't Romance Proper in it.
Werecockroach by Polenth Blake. Alien invasion/animal shapeshifter story. Novella. Zany and fast-paced. Aroace agender protagonist like the author.
And What Can We Offer You Tonight by Premee Mohamed. Sorta dystopian strange fantasy in an urban setting. Novella. The main characters are sex workers of the high-class courtesan prostitute type, and after one of them is murdered by a client, she comes back to life - and sets out on a whirlwind of freedom and revenge and justice she never got while alive.
Princess Floralinda and the Forty-Flight Tower by Tamsyn Muir. Novella. Fractured-fairy-tale fantasy. Told in a snarky, sardonic style, not nearly as upbeat as it initially seems.
The Black God's Drums by P. Djèlí Clark. Steampunk-fantasy. Novella. YA-ish? Steampunk New Orleans and a Black girl who can talk to the Orisha falls into a plot to steal a scientist's superweapon.
Elatsoe by Darcie Little Badger. Urban fantasy, YA. Urban fantasy in an all-myths-are-real kind of sense from a Lipan Apache perspective, starring an Apache girl who can talk to ghosts trying to solve her cousin's murder. Asexual protagonist with no interest in romance or partnering; it's refreshing and the sort of YA I would have loved as a teen.
HAVEN'T READ THIS BUT I KEEP MEANING TO
Firebreak by Nicole Kornher-Stace. Cyberpunk. No romance at all. VR and stuff. NKS is aroace and centering non-romantic experiences was her explicit goal here.
SOME ROMANCE BUT IT'S NOT A MAJOR FOCUS
Synners by Pat Cadigan. Cyberpunk. A kaleidoscopic whirlwind of a book with lots of characters with lots of varied relationships; romance is among them but not alone and certainly not the focus.
Three Parts Dead by Max Gladstone. Urban fantasy, sort of - it's like a fantasy-kitchen-sink world with gods whose contracts power the magic in the world, so magicians are lawyers and lawyers are magicians and one lawyer-magician has to solve the murder of, and resurrect, a murdered god before his magic grinds to a halt and the city powered by his magic collapses. I'm not doing this description justice - it was vivid and compelling. The main characters do not have any romance, but a supporting character has a toxic ex she can't fully get over that features as a sideplot in the story.
Finna by Nino Cipri. Weird, universe-hopping science-fantasy. IKEA has a tendency to rip open portals to other universes and the minimum wage employees gotta deal with it. The two main characters were dating but have recently broken up, and they don't get back together but rather figure out how to be friends again after the breakup.
Ninefox Gambit by Yoon Ha Lee. Military sci-fi space opera with a vast and interesting world and a very violent war. A military captain breaks rank and defies orders, so as punishment she has the digital ghost of a long dead war criminal downloaded into her head and she is pointed at a rebellion and told to crush it. I love Kel Cheris. No romance but some flashbacks to sex and sexual coercion.