You will need some extra hardware, but it will be possible to messsage and share GPS if the board supports it, or even walkie talkie style voice messages on some firmwares
You're right, there's no description in the post, and very little description in the repo. A lot of words about a patch, a patch, a patch, but a patch to what exactly? It says of game, but what kind of game, how does it look, what are the cool things about the game, you understand me 😄
You need to use authelia's oidc, and your nextcloud app will be able to store this session for everything it needs