Only a PC (or Raspberry Pi) running Linux (Ubuntu / Debian / Raspberry Pi OS) with an internet connection is required. No special hardware is needed. pacmd load-module module-null-sink ...
The algorithms, source code, look-and-feel of WSJT-X and related programs, and protocol specifications for the modes FSK441, FT8, JT4, JT6M JT9, JT65, JTMS, QRA64 ...