coming back from the UK is very hard right now, you will need to spend 21 nights out in another country before you can come back to HK then you need to spend another 21 nights in QT and thats if you test negative on arrival. many are getting caught on arrival as positive, then you are screwed.
I wouldnt leave HK until you sorted out your PR here. you can easily get a visa extension while waiting for PR application.