Victron ships an alternative Venus OS Large firmware image for the Cerbo GX that bundles a ready-to-run Signal K server (and Node-RED). Installing it is a firmware switch plus one setting — no SD cards, SSH or manual packages required.

1. Update the firmware — On the Cerbo GX (or Remote Console), go to Settings → Firmware → Online updates and install the latest version.
2. Switch to the Large image — In the same Online updates menu, change Image type from Normal to Large, then check for updates and install. The download and install takes a couple of minutes and the device reboots.
3. Enable Signal K — Go to Settings → Venus OS Large features and enable Signal K. Installer access level is required to see and change this setting (Settings → General → Access level).
4. Open the Signal K admin UI — Browse to http://venus.local:3000, or replace venus.local with the Cerbo's IP address if mDNS doesn't resolve.
5. Secure and configure — In the Signal K admin UI set an admin password under Security → Users, enter the vessel details under Settings, and confirm the NMEA 2000 connection (VE.Can is preconfigured by default). This is where plugins such as signalk-cruisereport can then be installed from the Appstore.

Reference: Victron Energy — Venus OS Large image: Signal K and Node-RED — official manual, including supported devices and troubleshooting.