[LAU] ambix LV2 vs ardour?

Hi all, Anyone out there successfully using the Ambix (0.2.8) LV2 plugins with Ardour5? I am having problems loading any of the plugins into Ardour5. This happens with both the Fedora ardour package and the demo install from Ardour.org. The Ambix plugins do load, for example, in Qtractor, but not in Ardour. Ardour shows them in the plugin manager, you can select one, "Add" it and then when you do an insert it a panel pops up that says "the plugin xxx could not be loaded". Looking at the log I see (for example): [ERROR]: LV2: Failed to instantiate plugin file:///usr/lib64/lv2/ambix_converter_o1.lv2/ambix_converter_o1 The directory looks like this: ls -l /usr/lib64/lv2/ambix_converter_o1.lv2/ total 5068 -rwxr-xr-x. 1 root root 5171056 Nov 29 20:43 ambix_converter_o1.so -rw-r--r--. 1 root root 5504 Nov 29 19:50 ambix_converter_o1.ttl -rw-r--r--. 1 root root 901 Nov 29 19:50 manifest.ttl -rw-r--r--. 1 root root 378 Nov 29 19:50 presets.ttl I built the plugins according to the build instructions, and nothing weird is shappening there that I can see (the build uses a recent lv2-devel package, etc). All the Ambix standalone applications that are also built work just fine with jack. Any help appreciated! (I have students that want to use them... :-) At some point in the past this was working but I don't know how recently this broke (I think this was fine in Fedora 24, it is broken in my tests on both Fedora 28 and 29). Thanks in advance! -- Fernando