If you switch to the new stack, most of the software is located inside the docker images and not on the host. Which means that you should jump in to a shell inside the container and run it there instead of on the host.
sudo docker exec -it satnogs_satnogs-client bash
then inside that shell that should look something like: satnogs-client@00e0894cb01c:/usr/src$ you can run SoapySDRUtil, this will also test that is is reachable from the container as well.
Checking the logs with sudo docker logs -f satnogs_satnogs-client