@brahma the suggested bios update is only for another model unfortunately.
The bios of the UM3402YA hasn’t been updatet since august of last year.
And the built in speakers sound awesome actually 
To buy some speakers isn’t really an issue, not being able to enable audio on the other hand is saddening, especially when others seem to have managed to do it.
@Giorgi23 If you don’t mind you could ask if someone can upload a working kernel maybe, because for some reason we can not get it working. As you mentioned some of the patches are indeed included already, only thing that is not added yet is the one in step 4, sadly it did not solve it for me.