Hello

I've managed to send a file using Bluetooth. First to get bluetooth running again, I've reset the device.
After this, bluetooth service worked again normally.

As advised by @gpatel-fr, I've installed bt-obex using crackle.

crackle install bluez-tools

I've then opened 3 Terminal tabs to run these tasks in parallel:

Terminal 1

# To find the Android phone receiving the file
bluetoothctl
scan on 
# Find and copy the MAC address of the Android bluetooth adapter to paste it in terminal 3

Terminal 2

# Start the obexd tool
/usr/libexec/bluetooth/obexd

Terminal 3

# Make sure that the Android bluetooth device is discoverable
# Send the file with bt-obex
bt-obex -p [MAC address of the Android bluetooth adapter] /tmp/test-bluetooth.txt

On the Android device, make sure that you accept receiving the file from the Ubuntu Touch device and check that the content is sucessfully received.