I wrote:

>by happy chance we do have OSS option, which is simpler and portable
>and simply works.

Also, if you go with OSS, you need neither xfce4-volumed, nor
xfce4-mixer, because:
- OSS has its own mixer;
- volume keys can be configured to be used with it.

Frankly, I don't understand, why Open Sound System
option is marked DEPRECATED in menuconfig.