[LAU] sound with Scarlett 3rd Gen device?

Dear Linux audio people, I have a Scarlett 18i20 3rd Gen interface which I'm trying to use on a recent Samsung laptop with Ubuntu 19.04. The 3rd gen devices are apparently shipped in non-functional "MSD" mode, so I registered and activated the device using Windows 10 following the instructions on the Focusrite website. Tested it there with Ableton Live Lite (provided via registration of the device) and also Ardour. It works fine. To get it to work on Ardour it was necessary to use the ASIO driver in the Ardour audio configuration. I had removed ASIO4ALL before installing the Focusrite/Scarlett software as suggested, so perhaps this driver came with Focusrite install. Now with the device apparently configured and the routing done in Windows using the Focusrite Control software (i thinks that's the name, I had selected output channels 1 and 2 to connect with the monitors/headphone jack), I returned to Linux. The Scarlett device is detected by lsusb, qjackctl and pavucontrol. Jack runs with no errors when the Scarlett is selected as the i/o device and all the correct channels appear in the Connect window. No sound however is heard through the phone jack, nor if i plug the phones directly in to the output jacks at the back. I tested using VLC configured for Jack output and also with pd -jack. With jack turned off and with VLC audio out set to pulsaudio, I set the Scarlett 18i20 as the preferred device in pavucontrol. With VLC playing the output VU meter for the Scarlett is active in pavucontrol but there is still no sound coming out of the device itself. Has anyone managed to get a 3rd generation Scarlett to work on Linux? Can anyone suggest please what I can do? Thanks! Iain PS. i did see an unresolved thread on this list last year about a 3rd gen Scarlett. I'll send a message to the author to see if the problem was fixed.