@odo but it is the same problem, all resorts to keyboard focus fights.

I have the same opposite experience. Dealing with this on X11 seems pretty easy, just a single X11 call away, while on macOS and Windows it is more complicated.

It all depends on the implementation of the host and the plugins.
Some hosts will send raw keyboard events to plugins, some will send vst2/vst3 specific events, some will send none. And a few hosts change behaviour when a "give focus" button is pressed. 🤷