Screen resize not working in QEMU/KVM Plasma guest

Hi all. I’m running NixOS as a QEMU/KVM guest, but I’m unable to get screen resize to work correctly in virt-manager. I’m using the default (generated) NixOS KDE Plasma config to which I’ve added:

services.spice-vdagentd.enable = true;
services.qemuGuest.enable = true;

I’m also installing the spice-vdagent package explicitly. According to systemctl status, both qemu-guest-agent.service and spice-vdagentd.service started up without errors, but screen resize isn’t working. Any ideas?

I just tried the same thing with GNOME instead of Plasma and screen resize does work in that case so this seems to be a Plasma-specific problem. Suggests to me this is a bug.

Opened an issue: Screen resize not working in QEMU/KVM Plasma guest · Issue #239490 · NixOS/nixpkgs · GitHub