I was able to reproduce with two of my machines running unstable. xserver-xorg and xinit were removed during the upgrade and I wasn't aware.
I downgraded to xkb-data=2.35.1-1 lightdm=1.26.0-8 from testing repo and reinstalled xserver-xorg and xinit. That resolved the issue for me on both machines. I've never reported a bug before, my apologies if this is incorrect procedure. Regards, Sent with [Proton Mail](https://proton.me/) secure email.