Please consider packaging the latest jackd2 upstream, v1.9.12.
It includes an enhancement to make JACK_PROMISCUOUS_SERVER more
usable and secure (see https://github.com/jackaudio/jack2/pull/257).
JACK_PROMISCUOUS_SERVER can now be used without lowering umask of
the server or client, and furthermore supports group permissions.
So there's finally a sane way to run a shared jackd daemon from the
init service and let users of a particular group connect to it.
I'm a DD-- happy to assist if I can assuming there's some will to
get this in.