I've had an LG OLED C9 for almost 3 years. I don't believe I've ever seen an ad.

You can go into the Settings, poke around a bit, and turn off all the personalization/ad options. When I turn on the TV, it shows the last used input source. No ads or junk.

At least in my experience, and that of friends, WebOS is minimalist, fast, and easy to use. The settings are easy to adjust, with plenty of advanced options you can drill into--and all presented in an intuitive manner. Not to mention being orders of magnitude superior to the slower-than-molasses Android abomination on my previous Sony X900F.

If you're just using for Netflix, Amazon, etc. (or with an Apple TV--also built in now as an app), I'm not sure where you'd see ads.