If I had to use my Ham radio for discrete communication, I could cover it in an encoded digital signal in any analog voice contact. Hiding in plain sight.
That is the easiest. Otherwise, back decades ago we used direct sequence spread spectrum or Frequency hopping SS. It is right above the noise level and across a set of frequencies. If I was targeted, The communication now would be carried via internet and be transmitted on a remote transmitter online. There are hundreds of thousand now.