A quick tip that you can specify that games load the alsoft.conf for OpenAL from your snap by setting the environment variable ALSOFT_CONF:
apps:
my-game:
command: desktop-launch $SNAP/usr/games/my-game
environment:
ALSOFT_CONF: $SNAP/etc/openal/alsoft.conf
plugs:
- desktop
- desktop-legacy
- joystick
- opengl
- pulseaudio
- wayland
- x11
parts:
my-game:
after: [desktop-glib-only]
plugin: make
source: .
build-packages:
- libopenal-dev
stage-packages:
- libopenal1