I may not be much help but having various computers and sound cards that I have used in the past; this would be my 2 cents worth (others may have the 1$ solution).
My config:
FT857D - DRA-50 - 7 Port USB powered hub-HP Win11 computer.
Initially I had difficulties?in setting up this configuration as well as when I had other radios and SignalLink interfaces.
I fixed my USB connections of "audio" by naming (in WIN 11) my I/O ports and sound interfaces,e.g., HF and VHF so when the external equipment is turned on first the booting of the computer does not rename?or adjust the setting I made during setup.? At one time I also did not have sound in the waterfall until I renamed the?default names to my HF and VHF sound settings.? When I switch from VARAC to WinLink HF or WSJT everything?is working?fine.? If I switch to VARAFM (VHF) I double check that my waterfalls are working.? There are times I have to toggle from the HF sound settings to VHF to achieve sounds to activate the waterfall.? I have also dedicated this computer only for Ham Radio, so all windows system sounds are muted according to the "various" input and output sound settings only to allow the "named sound settings" I created in Win11.
Not sure if this helps Rory but sometimes fooling around with the settings one at a time?as associated with the com ports being used as well as the VARA settings to be saved helped me out of my troubles.
