Google constantly find ways to change things up for the better or is it actually to confuse advertisers and have a lot of merchants advertise on Mobile Apps as the majority will struggle to keep up with the changes. Or worse advertisers will never know you can exclude mobile apps. I personally manage eCommerce accounts and have found in all cases that eCommerce and Mobile App Ads never work. The consume a huge amount of budget with no sales.
Since December 2018 you could exclude mobile app placements by excluding all of them by adding the URL adsenseformobileapps.com.
However Google has now removed this function in favor of manually excluding all 146 categories. Better yet, they have not included a exclude all. So you need to manually check 146 boxes. That sounds like fun!
As of writing there is a quick and easy method in excluding all of them in one go.
Download Google Ads Editor, if you do not have it already.
Open your Google Ads Editor software and connect to your account.
A popup appears and click on ok
Now click on Post in the top menu, and a popup will appear to post all data. Here click on post.
You are all done.