There now seems to exist an app that can read Libre 3 and feed to Xdrip, APS. I want to try it soon. Unfortunately you still need the official spy app to initialize the sensor.
for libre 2 if you use the bluetooth mode. You actually would install the libre app for initialization and then deinstall it so that it doesn't interfere.
ED I think it was xdrip https://xdrip.readthedocs.io/en/latest/