hi Andrew,
I’m pondering options and I’ll follow your progress with interest. I’ve used WSPR and WSJT modes for vhf dx in the past. Generally I used a signalink between a radio and a PC or laptop. The radios used have been FT817 and IC703.
If your radio has an inbuilt “sound card” the computer can connect direct to that and use that as the interface to the radio.
I found this account of one option for digi modes on the Pi4. https://www.emdrc.com.au/take-some-pi-on-your-next-portable-operation/
I’ve been given a few other things to read by my local portable digital expert, Wade VK1MIC.
73 Andrew VK1DA/VK2UH