I have recently noticed a vertical purple line along my TCL Roku TV screen. We have a TCL 40-inch 1080p Smart LED Roku TV - 40S325, 2019 Model. The Roku TV model number is 8113X and it’s software version is 10.5.0. We purchased this in December 2020. It appears at all times, even when the screen times out and fades to black. I have tried restarting the TV, unplugging it for 60 seconds then plugging it back in, and checking for a system update (there was not a new update available).
Have you tried contacting the TV manufacturer to inquire further? I'd suggest starting there to see what options or suggestions they can provide. Each Roku TV manufacturer provides direct support and warranty services for their products running the Roku OS.