Double on screen keyboard after updating tablet to 20H2

Question

I'm working on kiosk-like kind of application, we serve it on Linx 1010 tablets, running Windows 10.

App may work both in kiosk mode (with explorer turned off) and window mode in some places, where devices are used in various ways (basically, they need access to browser or system).

Originally application uses TabTip to allow user interaction. Since version 1703 or 1903 (when the new keyboard experience was introduced) we've had to disable it (with registry entry DisableNewKeyboardExperience). Otherwise we ended up in two keyboards displaying in window mode, new - gray one, overlapping the one we already invoke. Since new experience can't work without explorer, we went for consistency, keeping our app to invoke the keyboard.

Then we've updated to 20H2 and got surprised by the 'new experience' once again. This manifested only on our Linx tablets, on PC this wasn't observed.

DisableNewKeyboardExperience appears to have no effect now and only thing that worked was removal of TextInputHost.exe, what caused the system to stick to the old keyboard we use (surprisingly now the system uses it as well).

Since manual removal of system files is a bit hacky for an application to run properly, so my question is:

Is there any way to completely disable the new keyboard experience, like it was previously possible through the registry, without removing TextInputHost.exe program and keeping old on screen keyboard for users to navigate through the system?

Additional information:
I managed to reproduce the issue with different application. I actually wanted to use it just to record how the keyboard behaves with our app, but turned out that one had the same problem. You can get one for tests here: https://www.screentogif.com

I also attach below gif to present the problem (running screen to gif application).
Tablet is running in normal mode, not a tablet mode and explorer.exe is started.
You can see two keyboards popping up (on the side I've selected input box at the moment)
The first keyboard can be dismissed. But then you can observe that I've clicked close button on the dark one a couple of times, but it does nothing. To get rid of it I have to click on input box one more time. Then the close button closed the keyboard as expected.

Answer 1

Does this problem started in the new build? In that case, if possible do a quick test and uninstall the latest update and see if the problem persist?
If yes, then open start and search for Feedback Hub app and report this issue.