Global menu not working for nethack-qt

Hi, I’ve installed

nethack-qt
Name            : nethack-qt
Version         : 3.6.6-1
Description     : A single player dungeon exploration game
Architecture    : x86_64
URL             : http://www.nethack.org/index.html
Licenses        : custom
Groups          : None
Provides        : None
Depends On      : gzip  ncurses  qt5-base  qt5-multimedia  libxaw  libxt
                  libx11
Optional Deps   : None
Required By     : None
Optional For    : None
Conflicts With  : None
Replaces        : None
Installed Size  : 5.33 MiB
Packager        : Unknown Packager
Build Date      : Tue 13 Jul 2021 00:17:30
Install Date    : Tue 13 Jul 2021 00:23:42
Install Reason  : Explicitly installed
Install Script  : No
Validated By    : None

from the AUR, which doesn’t show the menu bar in global menu, instead shows the menu bar in the window, like
Screenshot_20210811_194600
No other Qt app has this issue (yet). I know that KDE’s global menu can be buggy, but the only other apps with issues are GTK apps, and even they are working via workarounds and using appmenu-gtk-module.

KInfoCenter
Operating System: EndeavourOS
KDE Plasma Version: 5.22.4
KDE Frameworks Version: 5.84.0
Qt Version: 5.15.2
Kernel Version: 5.10.56-1-lts (64-bit)
Graphics Platform: X11
Processors: 2 × AMD E2-9000e RADEON R2, 4 COMPUTE CORES 2C+2G
Memory: 3.3 GiB of RAM
Graphics Processor: AMD STONEY
inxi -Fazy
System:
  Kernel: 5.10.56-1-lts x86_64 bits: 64 compiler: gcc v: 11.1.0 
  parameters: initrd=\844b20d9ed524b5381eba22db9ead574\5.10.56-1-lts\amd-ucode.img 
  initrd=\844b20d9ed524b5381eba22db9ead574\5.10.56-1-lts\initrd 
  root=UUID=1ade638b-2046-4deb-abf6-5d158ba55143 rw quiet loglevel=3 
  nowatchdog 
  Desktop: KDE Plasma 5.22.4 tk: Qt 5.15.2 wm: kwin_x11 vt: 1 dm: SDDM 
  Distro: EndeavourOS base: Arch Linux 
Machine:
  Type: Laptop System: HP product: HP Laptop 14-bw0xx v: N/A serial: <filter> 
  Chassis: type: 10 serial: <filter> 
  Mobo: HP model: 8324 v: 22.27 serial: <filter> UEFI: AMI v: F.28 
  date: 04/09/2019 
Battery:
  ID-1: BAT0 charge: 28.0 Wh (100.0%) condition: 28.0/28.0 Wh (100.0%) 
  volts: 16.6 min: 14.6 model: HP Primary type: Li-ion serial: N/A 
  status: Full cycles: 252 
CPU:
  Info: Dual Core model: AMD E2-9000e RADEON R2 4 COMPUTE CORES 2C+2G bits: 64 
  type: MCP arch: Excavator family: 15 (21) model-id: 70 (112) stepping: 0 
  microcode: 6006705 cache: L2: 1024 KiB 
  flags: avx avx2 lm nx pae sse sse2 sse3 sse4_1 sse4_2 sse4a ssse3 svm 
  bogomips: 5988 
  Speed: 1096 MHz min/max: 1100/1500 MHz boost: enabled Core speeds (MHz): 
  1: 1096 2: 1096 
  Vulnerabilities: Type: itlb_multihit status: Not affected 
  Type: l1tf status: Not affected 
  Type: mds status: Not affected 
  Type: meltdown status: Not affected 
  Type: spec_store_bypass 
  mitigation: Speculative Store Bypass disabled via prctl and seccomp 
  Type: spectre_v1 
  mitigation: usercopy/swapgs barriers and __user pointer sanitization 
  Type: spectre_v2 mitigation: Full AMD retpoline, IBPB: conditional, STIBP: 
  disabled, RSB filling 
  Type: srbds status: Not affected 
  Type: tsx_async_abort status: Not affected 
Graphics:
  Device-1: AMD Stoney [Radeon R2/R3/R4/R5 Graphics] vendor: Hewlett-Packard 
  driver: amdgpu v: kernel bus-ID: 00:01.0 chip-ID: 1002:98e4 class-ID: 0300 
  Device-2: Sunplus Innovation HP TrueVision HD Camera type: USB 
  driver: uvcvideo bus-ID: 1-1.3:3 chip-ID: 1bcf:2c9b class-ID: 0e02 
  Display: x11 server: X.org 1.20.13 compositor: kwin_x11 driver: 
  loaded: amdgpu,ati unloaded: fbdev,modesetting,vesa 
  resolution: <missing: xdpyinfo> 
  Message: Unable to show advanced data. Required tool glxinfo missing. 
Audio:
  Device-1: AMD vendor: Hewlett-Packard driver: snd_hda_intel v: kernel 
  bus-ID: 00:01.1 chip-ID: 1002:15b3 class-ID: 0403 
  Device-2: AMD Family 15h Audio vendor: Hewlett-Packard driver: snd_hda_intel 
  v: kernel bus-ID: 00:09.2 chip-ID: 1022:157a class-ID: 0403 
  Sound Server-1: ALSA v: k5.10.56-1-lts running: yes 
  Sound Server-2: JACK v: 1.9.19 running: no 
  Sound Server-3: PulseAudio v: 15.0 running: no 
  Sound Server-4: PipeWire v: 0.3.33 running: yes 
Network:
  Device-1: Realtek RTL8111/8168/8411 PCI Express Gigabit Ethernet 
  vendor: Hewlett-Packard driver: N/A modules: r8169 port: e000 
  bus-ID: 02:00.0 chip-ID: 10ec:8168 class-ID: 0200 
  Device-2: Intel Dual Band Wireless-AC 3168NGW [Stone Peak] driver: iwlwifi 
  v: kernel port: e000 bus-ID: 03:00.0 chip-ID: 8086:24fb class-ID: 0280 
  IF: wlan0 state: up mac: <filter> 
Bluetooth:
  Device-1: Intel Wireless-AC 3168 Bluetooth type: USB driver: btusb v: 0.8 
  bus-ID: 1-1.4:4 chip-ID: 8087:0aa7 class-ID: e001 
  Report: rfkill ID: hci0 rfk-id: 2 state: down bt-service: enabled,running 
  rfk-block: hardware: no software: yes address: see --recommends 
Drives:
  Local Storage: total: 465.76 GiB used: 237.37 GiB (51.0%) 
  SMART Message: Unable to run smartctl. Root privileges required. 
  ID-1: /dev/sda maj-min: 8:0 vendor: Western Digital 
  model: WD5000LPCX-60VHAT0 size: 465.76 GiB block-size: physical: 4096 B 
  logical: 512 B speed: 6.0 Gb/s rotation: 5400 rpm serial: <filter> rev: 1A01 
  scheme: GPT 
Partition:
  ID-1: / raw-size: 32 GiB size: 31.2 GiB (97.50%) used: 20.2 GiB (64.8%) 
  fs: ext4 dev: /dev/sda4 maj-min: 8:4 
  ID-2: /home raw-size: 200.54 GiB size: 196.89 GiB (98.18%) 
  used: 112.31 GiB (57.0%) fs: ext4 dev: /dev/sda5 maj-min: 8:5 
Swap:
  Kernel: swappiness: 10 (default 60) cache-pressure: 100 (default) 
  ID-1: swap-1 type: file size: 2 GiB used: 259.4 MiB (12.7%) priority: -2 
  file: /swapfile 
Sensors:
  System Temperatures: cpu: 36.4 C mobo: N/A gpu: amdgpu temp: 36.0 C 
  Fan Speeds (RPM): N/A 
Info:
  Processes: 166 Uptime: 5h 32m wakeups: 4 Memory: 3.28 GiB 
  used: 1.91 GiB (58.3%) Init: systemd v: 249 tool: systemctl Compilers: 
  gcc: 11.1.0 clang: 12.0.1 Packages: 1300 pacman: 1293 lib: 269 flatpak: 7 
  Shell: Bash v: 5.1.8 running-in: yakuake inxi: 3.3.05

Does anybody have a solution to the issue?

Did you try to start it via terminal? Maybe there is some error output that can lead you in the right direction.

Yes, I did. After typing nethack-qt, there is no output until the program is closed. When the program is closed, it shows the leaderboard. It’s always been like this in KDE.
However, in MATE in the past, when I set Qt theme to GTK2 using qt5ct, I got something like “this program is using setuid or setgid. GTK doesn’t support that.” and an ugly UI. A workaround was to set Qt theme to kvantum or fusion or windows. Are these somehow related?