onboard keyboard at the LOCK screen

Hi,
I am on Xubuntu 20.04
I want to have the Onboard (virtual keyboard) at the LOCK screen.
No problem at the login screen i can choose to show the virtual keyboard at the top menu.
But not possible on the lock screen. (see my screenshot) Nothing append even if i click on the mini keyboard at the right of the text box.
It's worked on Xubuntu 18.04 but not on 20.04

Is it normal ?

https://ibb.co/kczJ55w