As I said here, https://www.linux.org/threads/command-at.387/post-170579
Suggest you go to https://www.linux.org/forums/command-line.145/ and start a Thread there.
and welcome to linux.org
The same I have received while in my research.Have you guys looked in the repository for it? It's in the Ubuntu repo.
AT is a command that comes installed on Windows by default. Didn't know there was a Linux version too.