These are TWO issues together!
First: Bluetooth Audio Device Changer
as mentioned before, this is the reason for No bluetooth device present, Libreelec setup screen hangs an so..
Second: Broadcom HW/firmware issue with wifi+bt working together. This issue is present almost 5? years, maybe more.. With NO solution till today. There is some "fix", but for me is NOT working. Version: 9.0.0 Leila V18.
(fix, already implemented in Libreelec: RPi3: Bluetooth impedes wifi · Issue #1552 · raspberrypi/linux · GitHub)
What I suspect is a) absolutely wrong firmware b) HW conflict c) Wrong wifi/bt antennas design
You must buy some wifi or bt USB dongle and turn off one of the feature of Rspi onboard.
Issue #2 has been fixed, take a look at this and see if it helps.