Hello,
You may try to publish edge and use Rdweb, but in our practice, you cannot download a rdp file from edge.
https://learn.microsoft.com/en-us/answers/questions/834928/kiosk-remote-desktop-to-app
So, you may try to use multiple-app kiosk mode and allow download:
https://learn.microsoft.com/en-us/windows/iot/iot-enterprise/customize/multi-app-kiosk
If the Answer is helpful, please click "Accept Answer" and upvote it.