In short:
- Enable contrib, non-free and non-free-firmware software containers in Software & Updates app (also reachable from Gnome Software in the menu)
- Install proprietary NVidia driver and Vulkan Installable Client Driver:
sudo apt install nvidia-driver nvidia-vulkan-icd:i386
There is one NVidia driver available on Debian by default (525). That worked for me when I was using Bottles in Flatpak but it wasn't enough when using Lutris directly (to test another issue).
DXVK couldn't load because it couldn't use Vulkan features properly or something like that. I had to install the 32-bit version of the Vulkan Installable Client Driver.