Whatever I tried, (editing the registry, winaero tweaker), I couldn't get the classic alt-tab to work on Win10 2016 LTSB. The solution in the end was to simulate the Right-Alt Tap when pressing Left-Alt using the following AutoIT script. This works for me but may break certain keyboard shortcut combinations that involve both Left Ctrl and Left Alt...
#NoTrayIcon
#Region ;**** Directives created by AutoIt3Wrapper_GUI ****
#AutoIt3Wrapper_Run_Au3Stripper=y
#EndRegion ;**** Directives created by AutoIt3Wrapper_GUI ****
#include <WinAPISys.au3>
#include <WinAPI.au3>
#include <Misc.au3>
If _Singleton ( "My_Alt_Tabber", 1 ) = 0 Then
MsgBox ( 0, "", "Alt tabber is already running!" )
Exit
EndIf
Dim $LALT = 0xA4
Dim $RALT = 0xA5
Dim $TAB = 0x09
Dim $CTRL = 0x11
Dim $hDLL = DLLOpen ( "user32.dll" )
While True
If _IsPressed ( "12", $hDLL ) Then
_KeyDown ($RALT)
_KeyUp ($RALT)
_KeyUp ($CTRL) ; RALT Is actually Ctrl-Alt so must release Ctrl!
While _IsPressed ( "12", $hDLL )
;
WEnd
EndIf
WEnd
Func _KeyDown ( $KEY )
_WinAPI_Keybd_Event ( $KEY, $KEYEVENTF_EXTENDEDKEY)
EndFunc
Func _KeyUp ( $KEY )
_WinAPI_Keybd_Event ( $KEY, $KEYEVENTF_KEYUP)
EndFunc
{ALT}{TAB}
.