Keyboard lock works most of the time by default.

But try this in Quicknanbrowser: https://keyboard-lock.glitch.me/

It can't lock the Esc key, because it was already tied to the ExitFullScreen web action on the application level. The application developers are not aware of when Keyboard Lock is active or not, therefore they can't untie the keyboard shortcuts to support this.

Maybe the solution is to create a permission request, similarly to Mouse Lock?