I tried installing on a RP 400 using HDMI audio.
For jack to work with HDMI I need to use HDMI with fkms, otherwise jack will not run.
I assume this is a general issue and missing from the documentation.
So I changed the config from kms to fkms, and jack runs.
However with this change Patchbox shows a secondary desktop on the display instead of the primary desktop.
My question is, why, and how can I fix it.
I couldnt find a way to display the primary desktop.
And fkms should not have any influence on the desktop setup.