Virtual keyboard use with iPad does not work

[B-G-T]

The connection is made but no keystrokes are shown on the iPad.
The iPad onscreen-keyboard is hidden when connected and revealed when disconnected => the connection seems to be fine.

btvs.exe -Mode Wireshark shows not much bluetooth traffic between iPad and PC even when I type something on the hardware keyboard and BLE Explorer is in focus.

[thusharaabc]

Doesn't work with iPhone 6s (iOS 15.7.2). It connect, but no keystroke received