How to apply this to interactive Terminal buffers?

[GitMensch]

As all other coloring tricks I've found this only works on normal windows, not on interactive Terminal buffers.
My use-case is: Start a Termdebug Session (:packadd termdebug, :Termdebug prog) and have all inactive Windows dimmed.

So far this works only with the source window (even not in the Terminal buffers when I switch them to normal mode with N ...)

Any idea how to tackle this?