On 17/12/2023 01:54, thelma@sys-concept.com wrote:
> But the scary thing is I don't know what fix it and running as user: 
> alsamixer still does not allow me to save default sound card
> I select with F6.

You don't set a "default sound card" with F6. All that does is simply 
allow you to see the mixer controls of a different sound card.

You set your default sound card by using your desktop environment audio 
settings. In KDE, I click on the speaker tray icon and there I can 
select my default sound card and default microphone:

   https://i.imgur.com/Lz3Bfyk.png

Surely there's something similar in the desktop environment you're using.