It took more than a year, but still!
Finally the annoying Bluetooth problem is fixed!
The amp turns on Bluetooth after power on, reconnects to the smartphone automatically without manual pairing and the application works fine (there's some problem with application scaling on LG G7 due to screen resolution, but I can live with that).
Thank you for this update, Marshall!
Even if the process was soooo slow that the 1-year warranty ended, it's good to know that you didn't abandon this product :)
Honestly I thought that we won't get any updates and I was surprised to see the Gateway application update and checked the forum just in case.