After updating Proton Experimental from 10.0-3 to 10.0-4, Kingdom Come: Deliverance II exhibits severe DX12 rendering issues on NVIDIA Turing GPUs (GTX 1650). Symptoms include missing terrain, broken depth buffer (seeing sky/stars through ground), untextured buildings, simplified/repeating landscape, and intermittent map streaming failures.

The issue did not start abruptly with the update; intermittent fallback rendering and streaming issues were already present several days earlier, but Proton Experimental 10.0-4 made the issue persistent and severe.

OS: Linux Mint 22.x (Ubuntu 24.04 base)
Kernel: 6.14.x
GPU: NVIDIA GeForce GTX 1650 (Turing)
Driver: NVIDIA 535.274.02
CPU: Intel i5-9300H
RAM: 16 GB
Display Server: X11

Proton Experimental 10.0-4 (regression)
Proton Experimental 10.0-3 (worked acceptably, intermittent issues only)
Proton 9.x (launches, visuals degraded)
GE-Proton 10-29 (fails with D3D feature level 12.0 error)

Kingdom Come: Deliverance II
DX12 via vkd3d-proton

I confirm:

• [✓ ] that I haven't found an existing compatibility report for this game.
• [ ✓] that I have checked whether there are updates for my system available.

Symptoms

• Terrain not rendering or partially missing
• Sky/stars visible through ground
• Buildings rendering without textures (smooth placeholder materials)
• Landscape appearing overly simplified or repeated
• World map sometimes failing to load
• Behavior varies between launches (timing-dependent)
• No GPU crashes or system instability

Reproduction

1. Use NVIDIA GTX 1650 with driver 535.274.02
2. Launch Kingdom Come: Deliverance II with Proton Experimental >= 10.0-4
3. Start or load a game
4. Observe terrain, depth, and texture behavior

Expected results
Correct terrain rendering, stable depth buffer, proper texture streaming, and reliable map loading.

Actual Result
Broken depth buffer, missing terrain, fallback geometry/materials, inconsistent map streaming.

Workarounds Tried
: Clearing all shader and pipeline caches

• Reinstalling the game
• Switching Proton versions
• GE-Proton with NVAPI enabled
• Disabling esync/fsync (stabilizes launch and saves, does not fix visuals)
• Forcing DX11 (crashes)

Regression
Yes. Proton Experimental 10.0-3 worked better. Regression observed after update to 10.0-4.

Additional Notes
GPU and driver verified healthy (nvidia-smi, glmark2).
Other Vulkan/DXVK titles work correctly.
Appears to be a vkd3d-proton + CryEngine DX12 regression affecting NVIDIA Turing GPUs.