I found Perth offered the best sc when flying Qatar out of Oz. Haven’t looked again lately.
Otherwise as a general rule I aim to credit partner flights to BA or AA. Easy enough to keep points alive in those schemes currently. Domestic BA to QF was ok with 10sc per economy leg.
Not sure about all airports but I was still allowed entry to the BA lounge in Singapore even with my nonstatus number in the booking and showing my Qantas card.