OK. Here are some instructions from Gizmodo that will put the ISO onto the flash drive with a Mac... they won't make it bootable though... read on...

1. Open a Terminal (under Utilities)

2. Run diskutil list and determine the device node assigned to your flash media (e.g., /dev/disk2)

3. Run diskutil unmountDisk /dev/diskN (replace N with the disk number from the last command; in the previous example, N would be 2)

4. Execute sudo dd if=/path/to/downloaded.iso of=/dev/diskN bs=1m (replace /path/to/downloaded.iso with the path where the image file is located; for example, ./windows7.iso)

5. Run diskutil eject /dev/diskN, and remove your flash media when the command completes (this can take a few hours on slower drives)

Now... after you read all that, on the Gizmodo page it says that if you want to make it bootable you should use a utility called Live USB helper they link to (which isn't there any more) and use a Mac mounting tool (which isn't there either!) to force the ISO to mount on the Mac so you can copy the files over. So... that article may prove useful, but probably not. I can find other copies of Live USB helper out there, but they are all Windows executables.

One method that will work is to swap the hard drive out of the PC and into the Mac. Put your Windows 7 installation disc into the Mac optical drive, and install Windows 7 on that drive. Once it is up and running (don't worry about drivers yet), follow these steps.

1. Run Command Prompt as administrator
2. Type to Command Prompt: %windir%\System32\Sysprep\Sysprep.exe, and hit Enter
3. In sysprep dialog that opens, choose “System Cleanup Action” as “Enter System Out-of-Box-Experience (OOBE)”, select “Generalize”, and select “Shutdown Options” as “Shutdown”. Click “OK”
4. Sysprep generalizes now your Windows 7 setup and shuts down your computer. Do not run any other programs during this phase!
5. Remove the drive from your Mac. Put it back into the PC.
6. Boot the PC from sysprep generalized hard disk. You will notice Windows booting as if it was the first boot after installation, installing default and updating registry. One or two reboots are needed, depending on your system specifications
7. When Windows finally boots up, you will need to enter all information as if this really was a new, fresh installation

All that is from here, but it applies in this situation a well, since you would be moving a Windows 7 installation from one computer to another. Considering that trying to make a Windows bootable USB stick with a Mac requires tools that either don't exist any more or are not being developed any more... this second method will most likely prove more dependable.

tl;dr

$ sudo dd if=debian-12.8.0-amd64-netinst.iso of=/dev/disk4 bs=$(( 1024 * 1024 * 8))

You do not need any additional apps and you do not need to do any file conversions. Debian ISOs are built to be used directly by the dd command without modification (because the Debian release engineers are awesome like that!). And the dd command comes standard with all Macs since OS X has a BSD/BSD-like base to it.

1. Plug in the target USB drive.

2. Open up Disk Utility and find the USB drive on the left side. Right-click (command click) and select "Get Info". Do this for the TOP-MOST physical device. In my case, I am ignoring the "Lexar Flash" device. All the devices underneath that top-most device will be written over anyway.

   

3. Note the "BSD device node" assigned to this device. In my case disk4.

   

   NOTE: This will translate to /dev/disk4 in the Terminal. If you see disk6 in the info panel, for example, then it will be /dev/disk6 in the Terminal. Etc.

4. Open up a Terminal window and type the following command (enter your user's password when prompted):

   $ cd ~/Downloads
   $ sudo dd if=debian-12.8.0-amd64-netinst.iso of=/dev/disk4 bs=$(( 1024 * 1024 * 8))
   

   • NOTE: Change directory and file name of iso to match what you have. What I have here is just an example.
   • NOTE(2): If you get a message from the system that it can't read the medium anymore, click "Eject".
   • NOTE(3): If you do not include a bs=... option, the same action will happen but it will take A LOT longer. So this is recommended on any modern system that can easily afford a large buffer to speed things up (any computer made past 1995 lol).
   • NOTE(4): The fancy $(( 1024 * 1024 * 8)) is using BASH's built-in calculator and I'm setting it to 8MB, essentially. The command requires the input in bytes, so we just do the quick math to give it a large value in bytes.

This process is not specific to Apple Silicon and should work the exact same way on Intel Macs.