When we announced https://trello.com/c/HK7aikI7/59-add-authentication-allowed-origins, we did not support wildcard subdomains.
Let’s say your app needs to be able to authenticate Trello users across a wide variety of subdomains. You would register
https://*.my-app.com which would allow
https://other.my-app.com. Note if you also want to allow the root
https://my-app.com you will need to register that separately.