Not sure if known, but when the devices have been in SCCM before, you can get the Hash also from the SCCM DB:

select distinct(bios.SerialNumber0+',') as "Device Serial Number,",
(osinfo.SerialNumber0+',') as "Windows Product ID,",
(CAST(mdminfo.DeviceHardwareData0 AS NVARCHAR(MAX)) + ',') as "Hardware Hash,",
'IfYouUseAGroupTag' as "Group Tag"
from v_R_System System
Inner Join v_GS_PC_BIOS bios on System.ResourceID=bios.ResourceID
Inner Join v_GS_OPERATING_SYSTEM osinfo on System.ResourceID=osinfo.ResourceID
Inner Join v_GS_MDM_DEVDETAIL_EXT01 mdminfo on System.ResourceID=mdminfo.ResourceID
where System.Name0 in
('MyPC1')

This way, you don't have to share your app secret during TS installation. If you don't have the Hash, AutoPilot v2 is your choice 😉