Hello again. 

I apologize, my previous message wasn't very clear. 

Yes, that is exactly what I mean. The login screen of the Horizon client would stack/hold on the Smartcard dialog and await a user to put in their smartcard. 

What worked for us previously, was exactly that:

Igel OS 11 (Ver. 11.08.230) would run the Horizon Client (ver. 2206-8.6.0-20094634) with autostart, so the Horizon Client, along with the login UI was always present when the device was not used.
The Smartcard dialog would show up as the initial option, even without a smartcard inserted when the Horizon Client was booted, as there could be hours in between the boot and the next login from a user. The smartcard dialog would remain open until it was used, or manually closed via the "Cancel" button on the UI - which would then switch to the AD login option. 
There was no set timer on when the login dialog would change from smartcard to AD, and for our use scenario - it is not needed. This is due to the low amount of users not having smartcard access and that would manually login (low amount, but sadly still needed).  

As soon as a card was inserted, it was recognized via our authentication client and the user could immediately login with their pin code and gain access to their virtual desktop - not having to start the Horizon Client manually or even choose which virtual desktop to work on as this was already done. Reason for this is to ultimately save time for the end user - fx. nurses and doctors on a hospital. 

Same scenario when a smartcard was removed. The Horizon client would be closed upon removal and the login UI would reappear with the smartcard dialog showing and remaining on the screen.