Hi,
PilotPete, to upgrade the firmware you have to have Windows computer. As the files provided by the manufacturer can only be used with that operating system.
The file is available at:
https://www.dell.com/support/home/uk...-d6000/drivers
- When you do the update make sure you do not have anything plugged in to the dock.
- Connect the dock to machine running Windows and run the file downloaded from the website.
- Follow the wizard and once this has completed you can connect your dock to your Mac.
Also double-check if you have Supplemental Update for your macOS available, if yes then please make sure to apply it.
Best regards,
Katarzyna