I've got an LG Oled TV a little older than yours. Some time back I read about LG TV's experiencing power boaerd failures I went online and found -through LG- a serial number checker

Mine was in the 'at risk' catagory and so, LG arranged for a local TV specialist to come out to my house. They changed the board and I've had no further issues.

Might be worth looking to see if your model/serial number is affected

Good Luck with whichever method gets your TV repaired

John