Plugin setup dialog and "fan out" feature missing

Curious to know if anyone else has encountered this… Using Ardour 8.4.0 on Ubuntu Studio 24.0.2, I’m not getting the plugin setup dialog. If create a new MIDI track including, for instance, one of the AVL drumkits, the track is created immediately and I never see the dialog asking how I want the outputs to be configured. At least, I can fan out the outputs after the track is created (from the pop-up menu obtained by right-clicking the track name in the mixer strip).

However, with some plugins, I don’t see the “fan out” option at all. If I create an empty MIDI track, add one of the LSP Multi-Sampler LV2 plugins (DirectOut version), and open the pop-up menu, there are no “fan out” options at all. (I can only add those plugins after track creation because they don’t show up in the instrument list when creating a new track.) Any idea what might be happening here?