Install Windows on a System Already running Linux

How to add a Windows 11 install to an existing Linux setup tl/dr: 1) Make sure you have an older WIndows 11 iso (the one I used was 24H2, build 26100.1742), burned to a bootable usb flash drive. 2) Shrink your main Linux partition so there's enough free space on the drive to install Windows. 3) In your bios, turn on secure boot. 4) Boot the installer, follow the wizard until the 'Select setup option' page. In there, select 'Previous Version of Setup' 5) Keep following the installer steps, choose 'Custom: Install Windows only (advanced)'. Make sure, when prompted 'Where do you want to install Windows?', to select the free space you allocated. 6) After 'Installing updates', an error message comes up, which begins with 'Windows could not prepare the computer to boot...'. This is expected. Hit 'OK', 7) Hit the 'Repair your computer' link. Choose 'Troubleshoot', followed by 'Command Prompt'. 8) Use the 'diskpart' utility. 9) 'list volume' to determine your main NTFS volume number (it should already have a drive letter), and your 100 MB fat32 partition (to remove). 10) 'select volume [100MB fat32 volume number]' 11) 'delete volume override' 12) 'select volume [older fat32 esp volume number]' 13) 'assign letter=[next drive letter in alphabet after the main NTFS volume drive letter]' 14) 'exit' 15) 'bcdboot [main NTFS drive letter]:\Windows /s [esp volume drive letter]: /f UEFI' 16) 'exit', reboot, remove USB installer drive, boot into the windows installer. 17) (optional) you can bypass network selection at the 'Let's connect you to a network' page of the wizard. Use SHIFT-F10 to get a command prompt, then use 'oobe\bypassnro'. 18) Continue windows setup wizard. Choose 'I don't have internet' link if you went with the optional step above. 19) Once logged into your installed Windows, logout, and in your bios, disable secure boot. 20) From your bios UEFI bootloader selector, choose your Linux loader, and make it the default in your UEFI boot order. Log into your normal Linux account. 21) use 'sudo grub2-mkconfig -o /boot/grub2/grub.cfg' to regenerate your grub menu list, which will now include a windows option.