YouTube viewed through a desktop browser still shows the so-called “overlay ads” – as their name suggests, they appear on top of the video (at the bottom edge). These are annoying and even the YouTube team agrees, so they are about to be axed. Starting on April 6, this type of ad will no longer be shown to users. And it will no longer be available as an option in YouTube Studio. However, YouTube expects that there will only be a limited impact for most creators as these ads will be replaced with “other ad formats”. Overlay ads used to appear on mobile too, but that they were axed...
Source: https://www.gsmarena.com/youtube_will_stop_showing_overlay_ads_on_desktop_starting_next_month-news-57814.php