I have a homebrew hardware/software setup using an ESP32-based  "Modem-Teletype Interface Unit (MTIU)" and a modified MFJ RS-232 switchbox to serve as a digital connection between virtually any type of terminal, Baudot or ASCII, and any of my terminal units (HAL ST-8000, HAL ST-8000A, Dovetron MPC-1000, Flesher TU-300, Heathkit HD-3030) . I have a Model 28 teletype connected via a loop to RS-232 converter. AFSK from the selected terminal unit goes through a manual stereo switchbox to a USB soundcard which is connected to a mac mini. In the mac mini the audio is routed through Rogue Amoeba Loopback to SmartSDR which is controlling the Flex 6400M radio. Also running on the mini is a homebrew RTTY terminal program connecting the Silent 703 (or any other terminal device) to the MTIU. The terminal unit used in the video is the Flesher TU-300. It's kind of a convoluted setup developed over the years of experimentation with this forgotten mode of communication. Actually, RTTY is probably the only digital mode that you can still experiment with. There are still a few of us who communicate over HF with "heavy metal".