Audio Interfaces Under Linux
It may be time to edit the Requirements web page, where audio interfaces under Linux are recommended.
Among the top choices shown on that page are four M-Audio DELTA models that are considered "legacy" by the manufacturer, and as such are no longer available other than on the used or NOS market. As Ardour evolves, I would certainly like to use it on latest/greatest proven hardware, rather than an interface already a decade old.
I'm seeing some good things mentioned about the affordable U-Phoria line from Behringer, and I'm hoping those are suitable to function with Ardour.