I found a drum sampler, Sitala, that behaves exactly how I want in Ardour, exposing a stereo pair for each of its 16 pads. This does however create 16 tracks that I don’t necessarily need to see in the arranger view but would like to still have them visible in the mixer - is that possible?
Sorry, it is not possible. In extremely old versions of Ardour it was possible to hide/show tracks independently in the editor and mixer, but many people would get confused as a result, and we removed that possibility.