Comment 89 for bug 1181666

I believe that I managed to fix this on my machine. I'd suggest to anyone having this issue to check for and uninstall any workspace-related extensions in gnome-tweaks. Read on for more detail.

This problem appeared for me after updating to 19.04 from 18.10. Like everyone else, I could click on items in the top bar (date/time, dock icons) and they would respond as expected, but applications weren't responding to keyboard or mouse input.

It seemed that pressing the super key was triggering this, as things would work more or less fine until the application switcher overlay thing was shown.

After reading through this thread and seeing a lot of mentions of workspace extensions I remembered that I'd enabled the Workspace Grid extension via gnome-tweaks. Loading gnome-tweaks showed a warning indicator next to this extension, with a mouseover tooltip that read something to the effect of "problem loading extension." After removing this extension, things seem to work fine.