Proton supports it, but Valve says each game build needs developer enablement. Check the individual game.
SteamOS anti-cheat problems: why some games still do not work
An anti-cheat problem on SteamOS is usually a game-support issue, not a setting you can fix from the handheld. Proton supports some common anti-cheat middleware, including Easy Anti-Cheat and BattlEye. Valve also says individual titles require developer configuration or enablement. That last part is the reason two games using a similar technology can have different outcomes.
To place this factor in a title-level compatibility check, see SteamOS Compatibility.
What Proton supports
When this affects the next part of the task, use Proton on SteamOS to keep the check specific.
Some middleware can work
Valve documents support for Easy Anti-Cheat and BattlEye under Proton. This is a platform capability, not a promise that every game using those names works today.
Each game still needs its own enablement
Valve says Easy Anti-Cheat support must be manually enabled for the game build, and BattlEye-enabled titles require a manual configuration step. Players cannot perform those developer-side steps for a published game.
Why kernel-level anti-cheat is different
Proton runs in a Wine environment
Valve recommends user-space anti-cheat components because they can usually run in the Wine environment. It says kernel-space solutions are not currently supported. This is a technical boundary, not a Steam Deck setting.
Do not diagnose by the error message alone
A launch failure can also come from a launcher, a missing dependency, DRM, or a game update. Check the title's Steam Deck compatibility section before blaming anti-cheat.
What players can actually do
Check the current game listing
Deck Verified labels and compatibility notes show whether Valve considers the game Verified, Playable, Unsupported, or Unknown on Steam Deck. Read the reason shown for Playable or Unsupported titles.
Keep troubleshooting narrow
Install SteamOS updates, restart, and test the game without newly added Desktop Mode applications. If the title is blocked by anti-cheat support, a VPN, DNS change, or controller adjustment will not enable it.