Step 1: You press Win + R to open Run

Then you type: C:\Windows\System32\spp\tokens\skus

Step 2: You download SKUs of Windows 10 Enterprise LTSC 2021:

Download File after this article


Then you extract it and copy it to C:\Windows\System32\spp\tokens\skus (The local you open at step 1)

Step 3: You open cmd (run as administrator)

run-cmd-by-administration

Then you copy and paste these codes:

cscript.exe %windir%\system32\slmgr.vbs /rilc 
cscript.exe %windir%\system32\slmgr.vbs /upk >nul 2>&1 
cscript.exe %windir%\system32\slmgr.vbs /ckms >nul 2>&1 
cscript.exe %windir%\system32\slmgr.vbs /cpky >nul 2>&1 
cscript.exe %windir%\system32\slmgr.vbs /ipk M7XTQ-FN8P6-TTKYV-9D4CC-J462D 
sc config LicenseManager start= auto & net start LicenseManager 
sc config wuauserv start= auto & net start wuauserv 
clipup -v -o -altto c:\ 
echo

Done.

You can check again

Windows 10 Enterprise LTSC Key