I use virt-manager on Ubuntu 17.10.1 (both host and guest). Key grabbing won't work. That is, I can't do control tab inside the guest machine for example.
I discovered that it has to do with Wayland:
I've followed the entire discussion, and at the end they say that this problem is fixed for applications built natively for wayland. I guess virt-manager isn't, because it doesn't work for me.
How to grab keys in virt-manager using wayland?