This is simple face plate branded with the Home Assistant logo designed to cover a UK light switch back box if you replace you switch with a smart switch/relay.
I replaced the light switch in my office with a Sonoff ZBMINIL2 (pictured) which connects to a Home Assistant Green running a Zigbee network of lights and switches. I didn't want to leave the old switch installed so created this blank face plate along with the Home Assistant logo (because its blooming great)
The author marked this model as their own original creation.