- It is installed by default, can be manually started and works.
- However cannot be automatically started, since that would be a usability mess. One systray icon just for sdwdate per VM. So for most users at least two, for gateway and workstation. And and additional one for any additional workstation.
The only instance of sdwdate-gui in Qubes should run inside Whonix-Gateway. Any Whonix-Workstation that boots should register itself automatically inside Whonix-Gateway's sdwdate-gui. Then notify Whonix-Gateway about its status. And on shutdown, de-register from Whonix-Gateway.
In case of Whonix-Gateway reboot, it would have to ask all currently connected Whonix-Workstations to re-register and to relay their current status.
Whonix-Gateway and all Whonix-Workstations would result in new sdwdate-gui systray icon sub menus.
It should be possible to securely implement this communication protocol using Qubes qrexec.