Is additional isolation needed for inverter control circuitry?
I would run the DALI circuit on a grounded DC supply, the grounding gives you protection in the event of a failure of the basic isolation. and makes it safe and easy to probe voltages and signals.
This may require fuses to prevent large fault currents from entering the DALI bus
Once you get the grounded system working you may want to consider changing it to an isolated system using enclosures and controls that
have reinforced insulation.