I'll not kick around the issues we read at https://us.community.samsung.com/t5/TVs/Dead-TV-You-Won-t-Believe-This/td-p/3696 over repair, replacement and extended warranty costs. That is pretty well done.

The problem is that to repair this, there are no user serviceable parts so you have to have some background and skills in repair. You might go to samsungparts.com for the service manual and check if spare parts are there or at shopjimmy.com. Without spares, I wouldn't bother with the service manual.

No forum tends to diagnose the dead TV as without it being on your shop bench, with the service manual you can't be sure what it is this time.

What to do? Get repair estimates, compare to new sets and move along.