I have bought a retail demo unit from ebay and it worked fine. I was succesfull in removing the "Retail Mode" app, but then stupid me wanted to experiment more.
I have experience flashing V50 so I have tried LGUP with retail stock firmwares for US TMO and Verizon. It did not work. Then I tried lgup_cmd and it started cross-flashing the TMO firmware.
At around 80% the screen went completely black but the firmware flash ended successfully according to the tool.
Now the phone does not switch on at all and does not react to USB charger.
Is there any chance to unbrick?