First of all, I have a little experience fixing tv's, but when we face a problematic TV our first thought is always the PSU because is the mos likely to fail, but not always, with new TV's, especially smart ones, the main board may be the real problem.
Recently I fixed a LG smart TV, no image, no backlight, no audio, no nothing, only the standby LED. I though that the PSU was the faulty one, but not, I checked all the volatges and all were correct, the real problem was on the main board, I had to reflow the main chip, heating it and the TV turn on again.
I'm not saying that you have the same issue as mine, I'm just saying that the PSU it is not always the problem, if you have image but not backligh, must likely the caps on the inverter are faulty. But if you have similar symptoms as the TV I mentioned, the main board could be the real problem.
Note: I don't recommend you test the capacitors, just replace them, if the tv has a couple of years working it is pretty normal that caps fails, even if they look good physically.