There is a free trial of Neural DSP’s “Plini” plugin available here: https://neuraldsp.com/products/archetype-plini/
When the AU is hosted by Juce, it only accepts mono input, on the first input channel. Any audio sent on the second/right channel is ignored. You can switch the plug-in from Mono to Stereo mode, but this makes no difference.
If you load the VST, however, Juce properly sends stereo audio to the plugin.
The same AU hosted by other hosts accepts stereo audio properly.
ALSO: If we use OpenGL acceleration, and load Plini, the interface of our application and of Plini completely freezes up. With OpenGL turned off, everything works fine.
I hope you can fix this AU hosting issue in a future release!