The current dnv testbed uses port 22 inside containers for ssh connections. This is the command that's executed when starting the containers:
CMD ["sh", "-c", "rm -f /dev/shm/db /dev/shm/global_vm /dev/shm/vpe-api; /usr/bin/supervisord -c /etc/supervisor/supervisord.conf; /usr/sbin/sshd -D"]

After a fresh intallation of the shared TG for arm testbeds, the containers are using port 2222, consistent with the Dockerfile of the image (https://hub.docker.com/r/snergster/csit-sut/dockerfile):
CMD ["sh", "-c", "rm -f /dev/shm/db /dev/shm/global_vm /dev/shm/vpe-api; /usr/bin/supervisord -c /etc/supervisor/supervisord.conf; /usr/sbin/sshd -D -p 2222"]

It's possible that the images are different for aarch64 and x86_64, but that shouldn't be the case, since the Dockerfile is the same for both.