Dungeon Warfare 2 - no keyboard input (698540)

Everything else works well, including mouse support. However, not a single key press on the keyboard is detected.

I know the game isn't officially whitelisted, but I thought reporting can't hurt.

My specs:

Computer Information:
Manufacturer: Unknown
Model: Unknown
Form Factor: Desktop
No Touch Input Detected

Processor Information:
CPU Vendor: GenuineIntel
CPU Brand: Intel(R) Core(TM) i7-4790 CPU @ 3.60GHz
CPU Family: 0x6
CPU Model: 0x3c
CPU Stepping: 0x3
CPU Type: 0x0
Speed: 4000 Mhz
8 logical processors
4 physical processors
HyperThreading: Supported
FCMOV: Supported
SSE2: Supported
SSE3: Supported
SSSE3: Supported
SSE4a: Unsupported
SSE41: Supported
SSE42: Supported
AES: Supported
AVX: Supported
CMPXCHG16B: Supported
LAHF/SAHF: Supported
PrefetchW: Unsupported

Operating System Version:
Ubuntu 18.04.1 LTS (64 bit)
Kernel Name: Linux
Kernel Version: 4.15.0-33-generic
X Server Vendor: The X.Org Foundation
X Server Release: 11906000
X Window Manager: Xfwm4
Steam Runtime Version: steam-runtime-beta-release_2018-06-14

Video Card:
Driver: NVIDIA Corporation GeForce GTX 970/PCIe/SSE2
Driver Version: 4.6.0 NVIDIA 396.45
OpenGL Version: 4.6
Desktop Color Depth: 24 bits per pixel
Monitor Refresh Rate: 60 Hz
VendorID: 0x10de
DeviceID: 0x13c2
Revision Not Detected
Number of Monitors: 2
Number of Logical Video Cards: 1
Primary Display Resolution: 1920 x 1080
Desktop Resolution: 3360 x 1080
Primary Display Size: 20.91" x 11.77" (23.98" diag)
53.1cm x 29.9cm (60.9cm diag)
Primary Bus: PCI Express 16x
Primary VRAM: 4096 MB
Supported MSAA Modes: 2x 4x 8x 16x

Sound card:
Audio device: Realtek ALC887-VD

Memory:
RAM: 15846 Mb

Miscellaneous:
UI Language: English
LANG: en_US.UTF-8
Total Hard Disk Space Available: 904158 Mb
Largest Free Hard Disk Block: 775586 Mb
VR Headset: None detected

Recent Failure Reports:

The issue names no source files, tests, or entry points. Start by reproducing the missing keyboard input on the reported Ubuntu 18.04.1 and NVIDIA setup; done means Dungeon Warfare 2 detects key presses while mouse support continues to work.