The operator found the menu I said to look for: it offers DAKY, RTS and DTR. KY
is the CAT route, so DAKY is the setting that would enable it — which makes my
previous "this rig has no CAT keying command" too strong a claim to leave
standing, since it was drawn from a refusal at the DEFAULT setting.
The error and the settings hint now name DAKY first, and keep the serial line
keyer as the fallback. That order matters: the CAT route costs nothing, the
fallback costs a second COM port.
Marked as untested rather than verified — I have no confirmation that DAKY makes
KY work on this model, only that it is the option that should.