The Wii U 5.5.3 system update was released on September 3, 2018. This was released in Europe, North America & Japan.
Official USA change-log:
- Further improvements to overall system stability and other minor adjustments have been made to enhance the user experience
VersionData, DeviceEula and "key and cert files" titles were updated for all the regions.
Wii U Menu, System Settings and User Settings titles were updated for europe only, suggesting changes for GDPR compliance.
System update report(s):