You can easily cycle through the email attachments and save them to OneDrive or SharePoint and then download them from there. But I don't think there is an easy way to create them and download them without saving them to temporary storage first.
You can save the attachment to a data source - SharePoint, OneDrive etc. using Flow
and then in PowerApps use the Launch function to directly call the attachment file
Launch("url to file")
This will seem like a download option for the user
If this post helps, then please consider Accept it as the solution to help the other members find it more quickly
Check it out!
Fill out a quick form to claim your user group badge now!
Find out where you can attend!
Features releasing from October 2019 through March 2020
The largest Power BI, Power Platform, and Data conference in New Zealand