According to the Harmony remote database they do support the Stello Ai500. You'll have to enter the model number as I've typed it here, with a lower case i.
You can connect any of the Harmony remotes to a computer, go to this url, https://support.myharmony.com/en-us/compatibility and download the remote codes.
You can connect any of the Harmony remotes to a computer, go to this url, https://support.myharmony.com/en-us/compatibility and download the remote codes.