Hello,
Even though the compositor is set to opengl 3.1 none of the desktop effects are working. In fact some have even been removed from the system menu under desktop effects!!
What is going on?

I had the same thing after the last update.. It appears that KDE has disabled compositing because the service is causing crashes.

Go in to System Settings -> Display and Monitor -> Compositor.

You should see a message about how compositing is disabled. You can turn it back on. Then check "start compositor at startup".

I set the rendering back end to OpenGL 2.0

After that, my desktop effects are working again, and I've had no problems so far.

Yeah cheers for that. Theres another thing that the update borked too. When entering fullscreen on dosbox then exiting all the open folders are "squished" frustrating i thought they had sorted all that problem out.