Until I read Paizo's Starfinder source book Pact Worlds, I'd honestly, kind of, forgotten that the Pathfinder gods are still relevant in Starfinder. It's easy to forget. There's no Cleric class in the game, there's no differentiation between arcane and divine magic in the Core Rulebook, so you can fall into assuming that the gods aren't in the game. They are though, and there's even a whole section in Chapter 12 of the Core Rulebook about gods.
I admit that my understanding of fantasy space is entirely defined by Spelljammer, so in my mind the Crystal Spheres apply, at least to an extent, to Pathfinder and Starfinder as much as Forgotten Realms, Krynn, and so on. Each solar system exists within a great (metaphysical) crystal sphere. A pantheon of gods has power within its crystal sphere, and no influence outside. When you leave one crystal sphere and enter another, it's time to find a new god. It makes sense because that's what my Spelljammer books told me.
In traditional D&D, gods are significant in part because they help define the alignment, and explain the divine magic, of certain societies. You know you're dealing with really bad people because they worship Rovagug or Urgathoa, or whatever. In Starfinder, though, you don't expect to travel through the Drift, emerge in a previously unknown planet, and find that the inhabitants there just so happen to worship the exact same god as you did back home. For whatever reason, that just doesn't feel alien. Strictly speaking, I don't see why in a science fantasy game that's not something we can accept, but I agree that for some reason it just feels unlikely (but the Drift and alien life and gods and magic? totally believable.)
I thought, initially, that Triune was meant as an allowance for religion in a science fantasy setting. There's evidence of this because Triune's broadcast of the recipe for Drift travel was received by every planet in the Pact World system, plus the Kasath and Shirren (both of which are well outside Golarion's system). So Triune is obviously a universal god, and I was ready to accept that for the sake of simplicity.
However, upon re-reading the section Faith and Religion in Chapter 12 of the Core Rulebook, it's clear that the Pathfinder gods, plus a few new ones from core planets, are very much spread through the Pact Worlds, and Triune is but one of them.
So I think the shortcut is this: Triune can be a universal god to save you from having to invent a whole new pantheon for every single planet your players visit, and for Pact Worlds the gods of the Core Rulebook also apply.
That's a nice quick fix to have, but what about a universal evil god? Personally,
In other words, having a universal god is handy when expanding the game board to include the entire universe. I do feel like a universal evil god is missing, but to my mind the answer is Nyarlathotep (I'm biased for my love of Lovecraft) or any outer god (I'm biased for my love of Lord Dunsany.) Nyarlathotep specifically is a Core Rulebook god, so he's an easy fit, and in a way a perfect antithesis to Triune. What's worse for the "All Code" god than an evil god otherwise known as "The Crawling Chaos"? As someone in the IT industry, I can definitely attest that the crawling chaos accurately describes most bug reports I deal with on a daily basis.
If none of that works for you, then of course there are plenty of great pantheons you can borrow from. As a GM, my problem has never been a shortage of gods, and in fact I have so many great pantheons I want to use but haven't had the opportunity. What better use than strange new worlds?
Here are 9 books of deities and demigods you could use with Starfinder:
And those are just the one's I've read!