How much risk is there in a separate-ticket international-to-domestic connection at Brisbane?

If you retain the tight connection, travel with documents ready and monitor both flights. Do not rely on the first airline to rebook a separate domestic ticket if its flight runs late.

Ask the domestic airline about its current check-in deadline and change policy before booking. A later flight or overnight stay may be cheaper than replacing missed tickets.

Treat two separately ticketed flights as two journeys. Build time for immigration, baggage, biosecurity, terminal transfer and the second airline's bag-drop cutoff; the scheduled gap alone cannot guarantee success.