I received a mail today titled AdMob starts implementing support for app-ads.txt files
Ensure that the app - ads.txt file is exe
The best solution i found is using Firebase Hosting (for FREE)
Then you don't have to have a website/domain for your app-ads.txt. You can host it for free on Firebase.
here is a HowTo from Google on how you can achieve this. Publish app-ads.txt with Firebase Hosting
The beauty of this solution is that you can still redirect to Firebase Url created to any website you want.
For instance in you Google Play account, you published the URL of your social Media as you website. without the redirection you have to put the Firebase URL there, but with the redirection, you can still have your own Website/URL in the Google Play Console and redirect the firebase URL to it. the user will not see any difference or changes.