UltraVNC

UltraVNC_1823_x64_Setup.exe installs expired certificate into:
C:\Program Files\uvnc bvba\UltraVnc\ultravnc.cer

Uninstalling an EXEMSI installation remotely with no GUI is not possible as the .msi uninstall command will just start the unins000.exe user interface.
so any commands for remote uninstall will fail

like those examples:
----
MsiExec.exe /X BD73903D-C694-4358-8F07-E71ABC89368F
msiexec.exe /x ...

Fixed in the flowing commit

Vnc viewer textbox size
https://github.com/ultravnc/UltraVNC/co ... c1ad3ca617

VNC server textbox size
https://github.com/ultravnc/UltraVNC/co ... b304634ba2

The previous native MSI installer from "UltraVNC_1436_X64" was better and signed.
The new UltraVNC - UNREGISTERED - Wrapped using MSI Wrapper from www.exemsi.com 1.6.4.0 is worst without signature.

You can read the help file here:
https://uvnc.com/webhelp/connections.html

In UltraVNC settings under "Connections" Tab you can select the following:

Query on incoming

A query window is a message box that ask permission to take over the control. You can select the timeout the default action ...

Yes but if you uninstall it after the MSI installation the service is not deleted and you need to run:

I can confirm that the UltraVNC_1435_X64.msi installer doesn't register uvnc_service as service.
The "UltraVNC_1435_X64_Setup.exe" is working fine but not the .msi package.

When the connection is over VPN with improperly configured MTU and MSS it also can cause gray screen. To test this you can use Wireshark and inspect the traffic for drop packets because of DF bit. Only for the test you can restrict the PMTU on both client/server which will limit the packet size to ...