When undergoing cancer treatment, I missed the launch of [Wayback/Archive] Ventoy:
Ventoy is an open source tool to create bootable USB drive for ISO/WIM/IMG/VHD(x)/EFI files.
With ventoy, you don’t need to format the disk over and over, you just need to copy the ISO/WIM/IMG/VHD(x)/EFI files to the USB drive and boot them directly.
You can copy many files at a time and ventoy will give you a boot menu to select them.
Source code: [Wayback/Archive] GitHub – ventoy/Ventoy: A new bootable USB solution. (2020 new, that is, but for me it was actually new)
Wikipedia: Ventoy – Wikipedia
Note there is also [Wayback/Archive] iVentoy, which is a PXE boot tool, but only partially open source and if used commercially you need a license. See:
The Wiert Corner - irregular stream of stuff 