Just a short information: At the end of September 2019, Dell released a BIOS update for its Dell OptiPlex 7070 systems. This provides support for downloading recovery images from the cloud.
On Friday, I became aware of a tweet that addresses exactly this issue.
Interesting new Dell BIOS feature. pic.twitter.com/UMUmTHS0Pk
— Steven Kister (@StevenKister1) October 4, 2019