Comment 1 for bug 1787267

That key actually exists on my german keyboard :-)

It would be:
< - no modifier
> - with shift
| - with right alt (also called alt-gr)

I'd not at all see why your setup goes for a EU keyboard mapping in your setup, but you might try "right-alt + <that key>".

Qemu doesn't "do" anything there except passing through.
I'd more assume that might be an option of your VNC client, did you upgrade the system the VNC client is on as well at the same time?