Ardour 5.3.0 can't connect to JACK session.
On a Debian / Jessie computer, I once custom-compiled Ardour 5.3.0, and tried a few tests with it, successfully always using the ALSA back-end. But, I had compiled Ardour with JACK support as well.
Much more recently I discovered, that this same version of Ardour, can't seem to connect to a running JACK server (v2). Further, allowing Ardour to start JACK on this machine is not advisable, because this machine already has PulseAudio installed, which I intend to keep, but which QJackCtl can suspend correctly.
Several other programs - such as QTractor - can use JACK just fine on this machine, for which reason I'm assuming that JACK itself is working.
But when I try to start Ardour with JACK, I get a hung window, the GUI of which is just unresponsive - and parts of which don't display correctly. Starting Ardour from the command-line this way, produces no error messages.
Do people have any hints for what might b going wrong? I could just continue to use Ardour on this machine, with ALSA, but out of principle, would also like JACK support working.