Hi, so I am having the same problem. It seems a recent update has broken a program that was working before. Not sure which of the recent updates caused these issues.
I have a program that worked great. I built it using the latest BT LE extension (20190701). I still have old versions of the .apk file saved on my phone and when I reinstall them, I can still find and connect to Bluetooth devices no problem. However, when I recompile the same program now, without making any changes, my device list never gets populated with anything. So it seems old versions of the .apk work fine where new versions have trouble discovering BT devices or properly building a list of the devices.
I figured I would test my list ("ListBLE") and populate it with a hard coded list rather than Bluetooth devices. The list populated my hard coded list, making me think it is an issue with Bluetooth LE.
I imagine you'll ask for this:
My phone is a Galaxy S10+