I’m doing something similar - and its working for me
because I want the Jenkins container to work with any docker.sock, I’m using a script like
https://github.com/SvenDowideit/docs-automation/blob/master/jenkins/setup-docker-and-start-jenkins.sh to create the docker group in the jenkins container, and then add the jenkins user to it.
perhaps the container’s docker group does not match the host’s one?
or maybe you have SELinux, and need to give the container SELinux permission to access the HOST’s socket.