SamyGO

The changes are persistent and yes the TV still reboots itself. I had also tried unplugging the electricity for a while.

"Actually any of known methods will help " do you mean any known methods won't help?

Also I am wondering if it is still possible to root the TV, however the remote control I have does not have access to smarthub.

25 seconds are not enough to do something even with rooted tv. Root possible only via widget way OR via channel list import procedure (sure, SamyGO widget shoudl be there already). Let say you have time to import channellist from specially prepared USB disk and let say you install hospitality mode hack. Then probably you will have time to access console and do something. But i doubt you can even mount external USB until TV goes to reboot. Upset.

Yes, i meant we do not know any way to unbrick TV from such state.

;(

Well thank you very much for your time in any case. I find it very sad though that a software issue means that hardware has to be thrown away (at least the controller), because Samsung doesn't openly offer proper recovery options...

At least I finally got around to playing with I2C, guess one always has to view the bright side of things

I will see if anything can be done with the remote control though, even though I also doubt it...

You can buy mainboard and get tv back to live second hand mainboard costs less and works well (confirmed by me self)

Well I have been looking at motherboards and will try that option, I think I have found one BN-01587B (mine is a BN-01587E). My panel is an LTJ400HV01-J so if people with similar TVs here could be so kind as to open their service menu's and report if their motherboard is compatible I would be grateful, just to get a small list of compatible motherboards

and thank you again juusso, I think I will choose this option especially since I can be sure that the motherboard is broken.