Stellar Odyssey

The developers describe how their game uses AI generated content like this:

This game makes use of AI-assisted tools in the creation of certain visual assets. All AI-generated content has been manually reviewed, edited, and adapted by the developer to fit the artistic vision of the game.

Required on Steam store pages since 2024. It covers content that ships in the game, on its store page or in its marketing — Valve does not require a disclosure for AI tools used during development, so this says nothing either way about how the game was made. Check it on Steam.