QR904, the Saturday 15 August 2026 2020 hours DOH-MEL (B773ER A7-BEI) was in the sky at 2117 hours, so Sunday 17 gate arrival should be around the 1735 hours mark, 45 behind. QR905, the flight back to DOH is the 2245 hours.
The BNE-bound (also naturally ex Doha) QR898 (A7-BEU, same model) is very similar, with this 2025 hours departure up up and away at 2123 last night. Sunday 16 arrival at gate looks to be 1819 hours, 49 behind. The return flight, QR899, is not timetabled to depart until 2210 hours.
Given Doha is its hub, the timing of the return flights can be heavily influenced by facilitating reasonable connection times to locations such as LHR.
However QR's quite generous scheduled stays in Melbourne and Brisbane are wise irrespective, as in the event of late running of the 'down' flights from Doha to Australia, it increases the chances of returning DOH-bound flights being punctual.