I use Admob to monetize my apps and recently I added Facebook mediation. For Android it was verified already (it was a while ago and I honestly I don't remember how).
I see this information fo iOS:
Instructions Copy the line below and add it to your app-ads.txt file at https:// domain.com/app-ads.txt. We've included your business...
The thing is that I have this mediation on a Flutter app and I have no domain.
How can I verify this? How can I validate this?
You can Publish app-ads.txt with Firebase Hosting
Then release new version of your iOS app and add the link to iOS app Marketing URL in app store connect.