Steam Deck - SteamOS 3.5.2 Preview: The OLED Update - Steam News
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Note: This update is for the Steam Deck Preview channel, and includes new features that are still being tested. You can opt into this in Settings > System > System Update Channel. General Added support for Steam Deck OLED Removed spurious splash screen during reboot and shutdown

SteamDeck公式情報 SteamOS 3.5.2プレビュー：OLEDアップデート