Jack build doesn't seem to work anymore for me, saying Cannot connect capture (input) port. I think it's because it tries to start jackd by itself and it conflicts with pipewire's jack client.
Either that, or now it treats the inputs literarly, I used to connect the inputs to stereo tool's outputs since it was a dead source, then the input program will connect to jack sink "stereo_tool". Maybe try to add a null input.
LE: I see that the jack sink name is now called "stereo_tool_jack_gui_64_BETA1002-051" instead of "stereo_tool", unfortunately still gives no audio.
LE2: Oh, just realized, the name of the jack sink/device and settings file are taken from the filename of the binary. I tried some different combinations but it doesn't fix it. Some very faint noise appears on the visualizer when i hit play.
I had some OS issues when testing it, but the output should definitely work - I've tested it with the tone generator in the FM output. For the input I have only been able to test silence so far due to those OS issues.
The new version only starts jackd if it's not already running, so that shouldn't make any difference.