I have found that my LG FH2 speaker uses the A2DP profile protocol:
http://gscs-b2c.lge.com/downloadFile?fileId=gQHBfK7s0ZXFVKL7CatPeA
...whereas my Android phone is unable to get connected to it, since it has a different profile AVRCP:
https://source.android.com/devices/bluetooth/services
Please note I am not trying to make my phone an audio sink, only audio gateway is totally fine for me.
¿How can I install, push, hack, or sideload via ADB such an A2DP Bluetooth profile so I can connect my mobile to my speaker?
Edit: it's a Redmi Note 5 global version (model M1803E7SH Latin America)