Sprinkle this in your mir-kiosk-XXX snap/snapcraft.yaml
mir-kiosk-snap-launch:
plugin: dump
source: https://github.com/MirServer/mir-kiosk-snap-launch.git
override-build: $SNAPCRAFT_PART_BUILD/build-with-plugs.sh opengl pulseaudio wayland
Where you put the plugs you need for your snap in the override-build:
command.
You use this to launch your app as follows:
apps:
daemon:
command: run-daemon wayland-launch XXX
daemon: simple
...
mir-kiosk-XXX:
command: wayland-launch XXX
...