Available from https://hub.docker.com/r/praseodym/unifi-armhf/ (docker pull praseodym/unifi-armhf).
Example Docker Compose setup (save as docker-compose.yml, run with docker-compose up -d):
version: '2'
services:
unifi:
image: praseodym/unifi-armhf:stable
restart: always
network_mode: host
volumes:
- /srv/unifi/unifi-data:/usr/lib/unifi/data