Well, you can use CW (continuous wave) which is basically using Morse code…not many people know Morse code any longer.
And the frequencies are different than usual commercial band radio.
So, they are private, but it would be very difficult to find someone transmitting without knowing a specific frequency and time.
…and the communications don’t go into servers or the cloud and so aren’t tracked like phone, email, internet, Twitter, or even blogs or websites.