Any scifi rpgs people can recommend aside from Starcrawler?

Are there others games which has a decent AI and decent turn based combat? (preferably on GOG)

That's quite a wrench in the works. How would a suggestion of X-COM with the Caveat of OpenXCOM sound?

Another shoutout for OpenXcom. Xenonauts and XCOM: Enemy Unknown are also incredibly good.

Robothorium

Phoenix Point

Star Renegades

Phantom Brigade

Space Haven

You can try Galaxy Squad. It is not very expensive and I like it. It is a mixture between XCom anf FTL.

You could give Incubation (part of the Battle Isle collection) a try.

Although it doesn't fit your description of "decent AI", but StarCrawlers does neither.

In Incubation enemies move in a very predictable pattern, and it's indeed part of the game to figure those out, the levels are like "tactical puzzles" if you get my meaning.

Try Stellar Tactics (in dev)

A nice traveller-like setting.

so which is it you want in the end?

Phoenix Point?

Halfway
Halcyon 6

Starcrawler is a Dungeon Crawler with turn-based combat, no tactics involved AFAIK.

Check out The Battle for Wesnoth. It's a free game - not free-to-play, proper free - and it's pretty good.

Like most people here, XCOM is the go-to sci-fi tactical turn-based combat game.

For 'other games with decent AI and turn based combat', I recommend:

Yakuza 7 (Like a Dragon) is phenomenal. It's a standalone story so you don't need to play the prequels and it looks absolutely gorgeous. It really is a stunning game. Runs like a dream too.

100/10, I highly recommend.

On Gog, you may want to take a look at those two titles:

Conglomerate 451

Halfway

Shadowrun trilogy?