I have an RPi4 + Kali + Piano 2.1 which I have had set to Dual Mono in the DSP settings and which combined with Volumio has been perfect for some time.
After a recent update the DSP Settings options changed and I can no longer select Dual Mono.
I don’t know what any of these options mean so it’s set to FIR interpolation with de-emphasis.
Set to Dual-Stereo and with connections to Left and Right RCA I get both channels working.
If I use alsamixer to set Dual-Mono (and reboot) with connections to Left and SubRight I only get the Left channel (nothing from either Right or SubRight).
Is there any prospect of the Dual-Mono setting returning to DSP Settings or making it work through alsamixer.