I'm running a dockerized Firefly III on a Raspberry 3 in my local network. With the help of an additional nginx Container and a self-signed SSL Certificate I was able to set up https.
Maybe somebody will find this guide helpfull, it took me a couple of tries to get it right.
Simply follow the official documentation at https://docs.docker.com/install/linux/docker-ce/debian/#install-using-the-convenience-script. You'll need to run the script if you are using the default Raspberry OS: Raspbian.
Use Pythons package manager PIP to install Docker Compose, details can be found on docker.com as well: https://docs.docker.com/compose/install/#install-using-pip. Before you can follow the guide you'll need to install python-pip.