I have stumbled across problem on Windows 10 LTSC 2019.
Domain users were not able to use Touch Keyboard. App TabTip.exe launched successfully, but keyboard did not show.
Whole problem was solved by adding this registry key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\TabletTip\1.7
REG_DWORD: [DisableNewKeyboardExperience] = 1
