Starcom: Unknown Space from Wx3 Labs, LLC has a fresh upgrade out now that brings in numerous improvements to the UI and controller support, as the developer hopes to get it Steam Deck Verified. Valve currently have it rated Playable.
About it: "Starcom: Unknown Space is an action adventure RPG of space exploration, ship building and fast-paced tactical combat. Enter a vast open-world universe filled with alien factions vying for power, strange worlds to explore, mysteries to investigate, and a sinister enemy that threatens the galaxy with an ancient power."

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Interestingly, the game getting a Native Linux version was originally a high priority. However, Proton has come a long way, so their updated FAQ notes it's still a goal but not high priority since it works well with Proton.
As for the "Kepler 21530 Controller / Deck Update", the developer said the "main goal of this build was to prepare the game for Steam Deck verification". Here's all the improvements it pulls in:
Deck/Controller Improvements:
General fixes:
- Improved Save & Load menus to enable all functionality via controller inputs, including toggling selections for delete, deleting old autosaves, etc.
- When text scaling is set to maximum (set by default on the Deck) all text should be a minimum of 9 pixels high at 1280x800 resolution.
- Eliminated areas where scaled text overlaps other UI elements.
- Dropdowns now keep current selection in view when using controller.
- All text input fields should bring up the virtual keyboard on the Deck.
- Now possible to toggle highlight, fog in map mode.
- Research panel correctly keeps research selection in view.
- In cases where there are two scrollviews visible (such as the ship log), right stick scrolls the first, dpad scrolls the second.
- Cargo screen allows for quickly analyzing items and proceeding to the next.
- Improved input handling in the shipyard.
- Chromaplate swatch customization now works with controller.
- Crew help should correctly reference controller inputs instead of keyboard if the controller is being used.
- If the player has set a "design goal", the trade screen previously did not show shortfalls in the faction's own reserve currency. Now it does.
- Rendering optimization when in map mode.
- Several minor typos.
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