Apple’s App Store has some ads. In my experience the first search result is always an ad, and every now and then the Today list features an ad. Not sure how much the normal data/results are skewed. It’s a store so you have to expect some kinda marketing tricks to sell you more. They tend to feature popular stuff.
It’s nowhere near as abhorrent as the post here.
I haven’t run into TikTok unless it has been featured or if it is the top result in the popular (free) apps chart. I wouldn’t dare searching for it 😆