I was wrong in my last post. The USB method was successful. I thought it didn't work because the Dell System Information (in Dell update) incorrectly told me that the BIOS was 1.1.24. After I exited and restarted  Dell Update it reported the BIOS as 1.1.26. So the USB method was successful. I agree that you are better off not installing a BIOS update through the Windows environment. The USB method accomplishes that, and does not use Windows at all. For the others that had the same issue, please try the USB method of flashing the BIOS.
I just tried installing Dell's new BIOS for my 8930 (Windows 11). It fails every time. I tried using the Dell Update app, which fails shortly after it says "installing" on the screen; and I also tried downloading the exe file from the Dell support website,  but when I start the exe, it immediately fails. I have never had a problem installing any of the other BIOS updates. Is there a problem with this update? Is anyone else having the same issue? Can anyone offer any suggestions?
XPS 8930, BIOS 1.1.26 fails