Is Dd not an option? I dont get why every distro need their own usb image writer when dd and ventoy already exist.

Unraid doesn’t use images you can download. They check the USBs UUID before installing. I am not defending this, but as it’s going to be the boot device for the server this is a little handy feature.

the unique GUID in the device’s rom is what they tie your license to.

unraid does have instructions and software as zip files for manually preparing a flash drive to run their software from. you don’t have to use their scary binary media creator tool. see here