Using Ardour 8.8.1 on Linux and to my surprise, there were no issues as far as the device recognition was concerned. This is also thanks to Linux itself. I did not have to do anything specific, it just worked, starting at the OS level !
Whereas on Windows I struggled and still have not succeeded !..
Anyone has a clue on what to chose as options for “Incoming MIDI on” and “Outgoing MIDI on” in “Control Protocol Settings” for the Novation Launchkey 4?
I did create a test MIDI track (see pic), so right now I can hear the sound of the keyboard on the monitor (although with a latency on the external speakers, as opposed to the phones connected to the same audio interface - UMC204HD).
Ardour has extended support for a number of devices. The Launchkey mk4 ones belong to that group. So Ardour basically looks at the names of the available devices, figures out if the names match the names of what there is extended support for, and then automatically enables the relevant control surface module and connects the device.