Q: Apple dropped support for Windows 8 on macOS Sierra?

W8.1 should still be supported. If you point to W8.1 ISO, do you get any error messages?

Can you post the name of the W8.1 ISO file and it's MD5sum?

Can you download the ISO from https://www.microsoft.com/en-us/software-download/windows8ISO using a wired network connection?

Please post the name of the file and the MD5sum after the download completes.

Your ISO is correct.

ls -lg Win8.1_English_x64.iso

-rw-r--r--@ 1 staff  4320526336 Dec  5  2014 Win8.1_English_x64.iso

 

openssl md5 Win8.1_English_x64.iso

MD5(Win8.1_English_x64.iso)= e0d4594e56c0545d379340e0db9519a5

What is the year/model of your Mac?

Can you create a USB Installer using Windows Media Creation tool on a Windows PC? We can add Apple drivers and then see if it will boot this installer. If it does, we can manually create a FAT32 partition and try to install W8.1.

haipowerfull wrote:

 

OK. But the thing is Mac use GPT format right?

The internal disk on the Mac is a GPT disk. It is unrelated to the external USB flash drive format.

Windows Media Creation Tool create MBR-format USB. I've done this before and it didn't boot

Can you connect the MCT-created USB to the Mac and post the output of

diskutil list

sudo fdisk /dev/diskN (where N points to the USB from the output of the previous command)

The FAT32 partition created on the internal Mac disk is a GPT partition also, but a Hybrid MBR can be built on the disk to install Windows using legacy BIOS mode, if necessary. Your 2015 Mac supports EFI boot since it is a UEFI Mac.