Devices, nodes and properties are being published at startup. Values are also being published at startup, but there's no formatting yet. Nothing else works ;)
Currently there's a cli to publish the extension to your zigbee2mqtt environment via mqtt.
pnpm install
pnpm run build
cd dist
node ./cli.js --help
When everything works and homie v5 is stable I will create a PR to get this into the zigbee2mqtt codebase as a built-in extension, just like the homeassistant extension