Hi. I am using the LG C9.
Have been using it to watch videos, animes and play games.
The TV has a lot of built-in features to prevent image retention and burn-in.
For example, the moment you put the TV in standby mode by pressing the power button on the remote, it will actually start to run a quick pixel refresher.
Also, when the TV is idling, the brightness of the content will start to be lowered. So something like if I'm on the PS5 menu, and the image is static, the brightness of the display will start to get dimmer. The moment you start making things move on the TV, it will get brighter again. You even have the option to lower the brightness of only a logo on the TV content that you are watching. So pretend I am watching Channel News Asia where the static logo is always shining brightly, the TV can detect that and lower just the logo's brightness instead of the entire screen as well.
There are a lot of safety measures that prevents the TV from getting temporary image retention. Letalone, burn-in.
I have the LG C7 and the LG C9. Using the C9 now as my main gaming display. I've played games like Persona 5 (which has a lot of bright vibrant colours) on the PS4 and have recently been playing Watch Dogs and Assassin's Creed Valhalla with my PC on this TV along with PS5 Spiderman Miles Morales now. Even with static HUD being displayed on the TV, you won't get permanemt Burn-in at all. As long as you vary your content, this is not an issue. I've been playing Valhalla for a week now. There are no burn-ins of the HUD in the game.
Checking my LG TV settings, it says that I've about 3857 hours of screen on time on the TV. And yup. No burn-ins even after more than 1 year of usage with this TV.

My C7 was from Jan 2018. That too has no burn-ins and it has been used by my parents to watch mostly TVs with a lot of static channel logos after I passed it to them since I got the C9