If you are running a mobile friendly site promoting app install ads, your site will no longer be considered mobile friendly.
“Starting today, we’ll be updating the Mobile-Friendly Test to indicate that sites should avoid showing app install interstitials that hide a significant amount of content on the transition from the search result page. The Mobile Usability report in Search Console will show webmasters the number of pages across their site that have this issue.”
After November 1, mobile web pages that show an app install interstitial that hides a significant amount of content on the transition from the search result page will no longer be considered mobile-friendly. This does not affect other types of interstitials. As an alternative to app install interstitials, browsers provide ways to promote an app that are more user-friendly.