When I try this it does not give me the option to keep settings - (Win8.1 Ent & Win10 LTSB is on same language & x64) Any suggestions ?
Don't know too much about this, especially 8.1 to 10 but I did 10 Pro to LTSB keeping all settings. As mentioned I've no clue if that will work for what you want to do - on your own head be it.
So I first did an upgrade to Standard Win 10 Enterprise & then used the registry hack above to upgrade to LTSB, just one thing it kept the Metro apps from the standard enterprise, but I removed them with the Powershell scripts. sfc /scannow said everything was ok so thank you Nucleus