CASUALTIES: UNKNOWN
BUILD 1.0.1

Platforms

The store record is Windows only. Mac and Linux are marked unsupported. Steam Deck's own report rates the game Playable, and the same report says the default controller layout is not fully usable. There is no Android, iOS, PS5, or Switch build in the platform flags.

PC requirements

Minimum from the store page
ItemValueStatus
OSWindows 10, 64-bitOfficial
CPUIntel Core i3-8130U 2.20 GHzOfficial
Storage500 MBOfficial
Display16:9, 16:10, ultrawideOfficial
Recommended64-bit processor and OS; no separate CPU/storage recommendation publishedLeft blank

Steam Deck

The Deck report category I am using is Playable. The same report says the default controller config is not fully usable, controller icons do not match the Deck, text entry does not open the on-screen keyboard, and interface text is hard to read. Performance and the default configuration check passed. That is one source, the Deck report, so I am not writing full controller support. The store categories I saw were only Single-player and Family Sharing.

Mobile, Mac, consoles

Android and iOS are not in the platform flags. macOS and Linux are explicitly false. PS5 and Switch are not listed. Spanish and Russian searches for a phone build land on this same answer.

Steam store screenshot 5 of Casualties: Unknown
Steam store screenshot 1 of Casualties: Unknown

Questions

Does it run on Steam Deck?

The Deck report rates it Playable and also lists controller and text problems. I would not call that full controller support.

Is there a Mac version?

The store platform flags say macOS is not supported.

Sources