Have you tried unplugging power and holding the power button for 10 seconds,?
Might, just be time to buy a new TV. (?)
If it turns on try disabling all hdmi cec features Try also to dlsconnect all devices connected through hdmi Mine did it because of hdmi cec bugs features
My old dumb LG TV did that and turns out the power cable/19V plug has gone bad. Visually the cable looks ok though. Standbys fine but dies when I try to turn it on. Try a new power cable?
I have had the exact same thing happen to my Samsung TV. Turns out it was a broken capacitor if I remember correctly. The symptoms were exactly the same...