Custom product pages are now available as ad target for search ads in App Store.

Apple Developer: Apple Search Ads now supports custom product pages
Apple recently confirmed that it buys ads for third-party apps and also communicates this practice to developers.
Initially, there were allegations that Apple is doing so in a "secret manner", however, Apple responded to allegations claiming that company keeps these ads for multiple years and communicates it to developers.
Apple says that the allegation that it is "secretly" or "quietly" purchasing ads for developers without their knowledge or consent is an overt mischaracterization. On the contrary, the company says that it regularly engages in conversation with developers about the ads it places and many developers express their appreciation for this support.
MacRumors