If you are staying in the airport, no portal required. I just did it on 8/26. Will do it again on Saturday and update if something has changed but I'm confident it hasn't changed.

You show your negative covid test at the Beef Island airport.

During your return to the US, after you clear immigration and customs you will be stopped by the National Guard before you can get on the elevator to the security area. You just show your connecting flight information and they allow you to pass without a portal approval.