Thanks a lot for this! Running Linux 5.4.2-1 (manjaro) and HX Stomp was detected with the your listed vendor and and product ids.
However I still can't get it working as an input with any audio application (ardour or audacity), but it shows up as an option.
I also have no PC output through the stomp (using only headphones, no speakers currently) with applications like spotify. alsamixer reports it as a soundcard with no controls.
My GUI sound settings lists it as "HX Stomp Analog Surround 7.1" and shows output levels being sent to the stomp, but I get nothing through the headphone out.