I still enjoy using the now deprecated Windows To Go [NOTE - despite Microsoft reporting as deprecated, it is still possible to create a Windows To Go drive manually, including with Windows 11 22H2].
Windows To Go was originally supported with the release of Windows 8, with a workspace creator used to create a bootable USB drive. Only fixed type disks were supported with the Windows To Go Creator wizard.
Manually configuring a Windows To Go device was possible with a combination of DISM + the bcdboot command to create boot files - and DISM can be replaced with alternatives including wimlib.
Back in the day when Windows To Go was released I had very limited hardware to test - I did not have any USB 3.0 disks or hardware with USB 3.0 ports. I was able to install Windows To Go successfully on USB 2.0 external HDDs. I also had a USB 2.0 flash drive that appeared to Windows as a fixed type disk - Windows To Go installed on this device but was effectively unusable due to the very slow speed (imagine wading through treacle).
I vaguely recall that my attempts to install Windows To Go on a removable disk failed during Windows setup - however I may be mis-remembering due to the passing of years. I have retried with Windows 8.1 Update on a removable disk (applied using wimlib + bcdboot) - setup failed on my Thinkpad T470s booting in BIOS mode (CSM enabled).
I was however able to apply and install Windows To Go based on Windows 10 21H2. So when did Windows To Go start working on removable USB drives?
I used a 32GB SanDisk USB 3.0 Ultra Fit. Windows 10 DiskPart was used to prepare the USB drive (Windows 10 version 1703 or newer is required to create multiple partitions on removable disks - with multiple partitions necessary to boot in UEFI mode due to the requirement for FAT32 for the boot partition/files (see NOTE1)) -
select disk # clean create partition primary size=1024 active format fs=fat32 label=USB-1 quick assign letter=r create partition primary format fs=ntfs label=USB-2 quick assign letter=s
wimlib was used to apply install.wim - this step was painfully slow! Example command -
wimlib-imagex.exe apply #:\sources\install.wim 1 S:
bcdboot was used to create boot files on USB partition 1 -
bcdboot s:\windows /s R: /f ALL
NOTE1 - FAT32 should be universally supported on UEFI firmware and a small FAT32 partition for boot files will ensure wider compatibility on different hardware. A NTFS boot partition may be supported on some hardware.