Windows 10 iso:

a) When downloaded from the Microsoft website can be used on computers that have BIOS Legacy or UEFI:
https://www.microsoft.com/en-us/software-download/windows10ISO
Download Windows 10 ISO File
Create Bootable USB Flash Drive to Install Windows 10

b) This Tuesday Dec 8, 2020 Microsoft has scheduled a cumulative update and an iso update
Windows 10 20H2 update fixes broken in-place upgrade feature

c) If there is a working computer and an internet connection Windows 10 iso are available for fresh downloads

d) There are websites that have older iso:
Microsoft Windows and Office ISO Download Tool
TechBench by WZT (v4.1.1)

e) This is a video and an additional method to create an iso from the Microsoft website:
Britec Uploaded a new video, Thought I would share it with you.

f) For possible boot failure consider making Macrium backup images and using Macrium boot rescue:
Macrium Software | It’s our business to protect your data
Backup and Restore with Macrium Reflect