Your setup
Short list, and you almost certainly have all of it sitting around already.
A node
Any Meshtastic or MeshCore device your phone can reach over Bluetooth, or one on USB serial if you play from a desk. Stock firmware. Nothing to flash, nothing to patch.
One channel, Meshtastic only
On Meshtastic the game uses a secondary channel called MeshTorry. The app
offers to add it for you. The key is derived from the name, so it is not a secret and is
not meant to be one. It just tells the game which packets are its own. On MeshCore there
is no channel at all, the game talks to repeaters directly. Nothing else on your node
changes either way.
The app
Android (Bluetooth or USB), or the web app in a Chromium-based browser with Web Bluetooth. Same game either way. The Android build works offline and uploads when you are back in coverage.
Get the Android app Open the web app
The beta is small and gated. You create an account, I read it myself, and if it's approved it unlocks within 5 days. If not, it's removed. See Apply as a tester.