Why this page exists: A handheld or controller player needs the current official boundary before buying or configuring controls.
Three different questions
A Windows build can run through a compatibility layer without having native SteamOS support. A game can also be playable by touch without full controller support. Finally, a player report is not the same as Valve's Verified or Playable rating.
The dated developer guidance
The developer said the Deck touch screen was the best option at that time and that controller support was not available. Another reply described controller support as planned, but future intent is not a shipped feature.
What to check before purchase
Open the live Steam store on the device and check its current Deck badge and input labels. This page intentionally does not claim a current performance profile, battery result, or full controller map.