VNC shows black screen in 15.4, OK in 15.3

In the last 24 hours I installed 15.4 Leap over 15.3. In 15.3 vnc worked correctly.
Using Wayland; my process was to run vncpasswd followed by vncserver in a terminal on the host
and then using VNC viewer on a raspberry pi view the remote machine.

After the update to 15.4 the same process no longer works. It seems to start up fine, I enter the password
at the client which connects to the host but then the viewer shows a black screen.

As a test I switched off Wayland and rebooted and used X11VNC server and was able to view
the remote screen correctly. The client is set to automatic wherever possible.

Is it possible that something has changed in the leap from 15.3 to 15.4?

Well Wayland is very much beta on KDE and things do change between versions :open_mouth: