Addendum: It is possible to make a channel selection from within $ alsamixer (see screenshot) and also add the soundcards own surround FX (upscaled stereo). That works, so the hardware can give output to the speakers. It seems, the “line out” profile acts as virtual mediator in this case.
But still the problems persist:
- No 5.1 channel output as per true audio signal
- No microphone level input
This problem obviously plagues all users of this soundblaster series (AE-5, AE-5 Plus, AE-7…). For now, everyone else literally gave up:
https://archived.forum.manjaro.org/t/sound-blaster-ae-5-5-1-surround-even-possible/113841/19