Deathmatch relies entirely on the Source engine's rigid body physics. On a Snapdragon 865, throwing a radiator through a window causes massive frame dips (from 60 to 25 FPS). The ARM port lacks the optimizations for "multi-player physics replication."
These videos demonstrate the setup process and gameplay performance of Half-Life 2 and Deathmatch running on Android devices: hl2 deathmatch android
Searching for this will bring up sites claiming to offer an APK. They often: Deathmatch relies entirely on the Source engine's rigid