When using APIM API URL Suffix Validation (".well-known") through Portal, a generic error is thrown.

Universal Links is common to Apple Mobile development, and you MUST host the file at <domain name>/.well-known/apple-app-site-association. It cannot be nested under further paths.

If the 2019-01-01 Azure RM API is called directly, ".well-known" works fine as the Path, so this is only an issue today with the portal and also in terraform. This may be a regression in the latest 2019-12-01 API.