I have the TCL 43S425-CA (2019) 4k TV. It randomly started doing an infinite restart loop and so I found this solution on the forums: https://community.roku.com/t5/Features-settings-updates/Bricked-TCL-43s405/m-p/589588/highlight/true...
I went to the Secret Factory Menu in Store version of the tv set up, and I accidentally clicked on an option called Image Switching. That completely bricked my tv by making the screen only show shades of white and grey. I cannot see anything else. I tried resetting the tv by clicking the reset button on the back but that did not help. I even spoke to support about this issue but they could not help me. I'm assuming there is a backup way to reverse the Image Switching option. Can I still save my TV?
Try pressing and holding that reset button for at least 30 seconds with the power connected.