I don't remember the key combination that worked, google it. I think it is "POWER (off) - INFO - MENU - MUTE - POWER (on)"
If you have a smartphone with a built-in IR you can use this app to get into the menu.
I don't think it would affect the warranty unless you explicitly tell them that you messed around with the Service Menu.
The submenu you are looking for should look something like this:
Hello @smp1 ,
Thank you for the info. However most of us don't have an IR remote controll and recent new phones have discontinued IR so it's kinda difficult to open the service menu but I have seen a technician open this with a simple samsung remote for older TV's.
Can you give us some more info about what side-effects the TV will have after we disable "Instant On" and "Always Instant On Support" ? Can I assume that after this setting, the TV will never go in stand-by mode and will always completely power off? I have noticed that even when I completely power-off the TV, when I turn it back on, the resolution indicator works just fine for a while and after a few hours it gets broken again.