[LAU] Using udev to launch JACK as specific user?

Hi. After 2 hours of "edit, reboot, fail" I am giving up and ask here. I feel like what I want should be relatively simple, but it isn't. I'd like to launch JACK via Systemd whenever a certain card is present. I have a udev rule in /etc/udev/rules.d/10-8A.rules that looks like this: ACTION=="add", SUBSYSTEMS=="sound", ATTRS{id}=="D8A", TAG+="systemd", SYMLINK+="MOTU-8A" This works, I get a /dev/MOTU-8A symlink. The idea was to declare [Install] WantedBy=dev-MOTU-8A.device in my systemd user service for JACK. However, contrary to what the web seems to document, the symlinked device does not show up in systemctl. So apparently, I can't depend on it either. I am guessing anyone here must have a similar setup. In its purest form, I am looking for a way to launch a systemd user service once a certain ALSA hw device is available. I see references to ENV{SYSTEMD_USER_WANTS}="jack.service", however, I totally fail how this should work. Udev has no idea which user should launch this service. Any hints to untangle this sort of messy situation? -- CYa, ⡍⠁⠗⠊⠕