Here is a guide for create a DaRT recovery media that allows for resetting the admin password of a Windows 10 machine. In this case it was a Windows 10 20H2 machine, where the admin password was not known, and the machine was in a workgroup mode too.
DaRT, or the Microsoft Diagnostics and Recovery Toolset, is part of the Microsoft Desktop Optimization Pack (MDOP), which is a great set of tools available as a subscription for Software Assurance customers. DaRT is primarily used to diagnose and fix a computer that cannot boot, or is having other issues starting. One of the tools included in DaRT is the Locksmith tool that allow you to reset passwords for local users on the device.
Install DaRT, and creating the DaRT Recovery Image
Creating the DaRT recovery media is a fairly straightforward process. You need to have the Windows ADK and the WinPE addon installed, and have access to a Windows 10 media since DaRT are using files from those. I have only tested DaRT with Windows ADK 10 2004.
Note: Based on heavy real-world experience I recommend using the same version of Windows 10 as the version you are about to recover and build media from. Otherwise, you may run into this error when generating the DaRT media.: Package is not applicable: 'C:\Program Files (x86)\Windows Kits\10\Assessment and Deployment Kit\Windows Preinstallation Environment\amd64\WinPE_OCs\WinPE-FMAPI.cab'
Anyway, after downloading the MDOP 2015 ISO from VLSC, mount the ISO and install MSDaRT100.msi from the DaRT\DaRT 10\Installers\en-us\x64 folder. Use the default settings for the install wizard
Note: If the installer is now showing the DaRT Recovery Image option, you are most likely missing the Windows ADK and WinPE Addon for Windows ADK on the machine.
Once the installation is complete, you can go ahead and start the DaRT Recovery Image tool from the start menu. Simply point it to where you have the Windows 10 media, and it will create a boot image for you. Either as a WIM file, or ISO, or both. Below are some screenshots of the process.
When the DaRT Recovery Image has been created, simply boot your device on it, and start the DaRT tools from the recovery menu. When the DaRT tools menu is shown, select the Locksmith option to reset the admin password. This is what it's look like: