I noticed the problem with 6.3 first a couple of weeks ago. When assigning Zynaddsubfx to a midi track the following happened
Within the Ardour environment calling up Zynaddsubfx took relatively long
Calling up the Instrument Bank, again takes a while , " the instrument bank has NO content and the zynadd… window disappears. so, I can´t select an instrument.
Calling up the virtuell keyboard … the zynadd… window disappears
I suspect the problem started with version 6.3. Upgrade to 6.5 did not solve the problem.
I am running opensuse Leap 15.2 (latest version.)
Thanks and have a Covid-free xmas