The return trip was planned as follows by my travel agency: QF9 flight departing at 22:55 on September 30 in Melbourne, arriving at 07:05 in Dubai (on October 1st). Then flight QF8073/EK73, departing at 08:20 from Dubai, and arriving at 13:00 in Paris. Then my travel agency reserved a train departing at 18h10 from Paris Gare de l'Est, to arrive back home in Nancy.
The QF9 flight, scheduled at 22:55 in Melbourne, with arrival at 07:05 in Dubai, did take off only at 00:50, with arrival at 08:44 in Dubai (cf insurance letter).
In Dubai, the QF8073/EK73 flight was already gone. We had to board at 14:30 into a first plane for the EK75 flight. After one hour spent into the plane, we were told the plane had a "computer problem", and we had to disembark. Another plane finally departed at 19:30.
We finally arrived in Paris (Charles-de-Gaulle airport) at 01:00 on October 2nd (instead of 13:00 on October 1st). We had no information from Qantas about how to complete our trip. There was no RER train any more to reach Paris Gare de l'Est, so we had to take a taxi. Since there was no train to go back into Nancy, we had to spend the night in our family in Paris. We took the train departing at 10:13 from Paris Gare de l'Est, and arriving around 11:45 in Nancy on October 2nd, instead of 19:47 on October 1st, thus with a total delay of about 16 hours.
We only asked to be reimbursed from the extra costs due to the delay, i.e., the taxi to go from Paris CDG to our family in Paris, and the new train ticket we had to buy on October 2nd (the original train ticket could not be changed).
The answer from Qantas was no. This is why I will never fly with Qantas again.