Wine (in the GE-Proton8-26 runner) uses its ALSA driver, which routes through ALSA’s default device. On the host, that works because Ubuntu’s ALSA config sends default to the pulseaudio plugin → PipeWire.

Inside the Flatpak sandbox, the same path broke at two levels:

1. The runtime’s ALSA default routes to the pcm_pulse plugin, which tried to load libwrap.so.0 (a tcp_wrappers dependency of pulseaudio’s libs) — and the freedesktop runtime doesn’t ship libwrap: ALSA lib: Cannot open shared library libasound_module_pcm_pulse.so (libwrap.so.0: cannot open shared object file) → audio device open failed → silent game. (The launcher worked because the host has libwrap.so.0.)
2. Along the way I also found the wine prefix had no explicit audio driver selection; I set HKCU\Software\Wine\Drivers → “Audio”=”pulse” in the prefix registry so the pulse path is used deterministically.

The fix (no root required)

• Copied the host’s libwrap.so.0 (4 KB) into /home/yves/Games/gog/bleak-sword/lib/
• Added LD_LIBRARY_PATH=/home/yves/Games/gog/bleak-sword/lib to:
  • the Lutris game config env, and
  • launch-bleaksword.sh (appended to any existing value, harmless on the host)

Now ALSA’s pcm_pulse plugin loads inside the sandbox, routes to the PipeWire socket (which the Flatpak already had access to), and the audio flows.

Lutris runs inside the Flatpak sandbox, where the host’s NVIDIA driver is invisible — Flatpak apps get it via a matching org.freedesktop.Platform.GL.nvidia-XXX extension. You had extensions for old driver versions (525/535/570) but not for 580.178.04 (the current host driver) — so inside the sandbox there was no NVIDIA Vulkan driver at all, and DXVK aborted instantly. That’s also why Lutris logged “card0” is No GPU.