Bluetooth is fixed!
Plus backport of NO_NEW_PRIVS is added into kernel for further Flatpak support but the kernel seems to be too old for that.
Unless we can patch the glibc for flatpak like I have done it for sailfish.

Edit:
The bluetooth is still needs some love because it starts only with the reboot (if it was switched on before that) and once it is on (after the reboot) and you switch it off, you cannot switch back on without another reboot. (Maybe the problem is the initialization.)
Plus when I paired with my bluetooth headset, the audio is not routed to it. (It still heard the sound from the speaker.)
So, I go back to the drawing board.