I know that this is a problem card, I also know that pulseaudio does not work well in Buster, but it is possible pulseaudio works less or less well in Elec. If so, then there are several possible solutions to your problem.
1. Use ALSA settings (yes, the audio subsystem has rich features)
This will cause difficulties if you have not worked with asoundrc, but it will solve many problems. Including it will save you from the clumsy and poorly working program of the German programmer, which still causes numerous problems with the OS (pulseaudio).
2. Turn on pulseaudio. This program is supposedly created specifically for such purposes (like yours), so the setup generally takes two to three minutes. Of course, if pulseaudio will work. And if you are comfortable with the sound.
Put the pulse control graphical interface and then the procedure will be very simple
3. Using jackd is a complex professional solution, but allows for delicate operations. However, the setup will seem complicated at first.
Of course, the easiest way is pulseaudio with a graphical interface. L