Following my last message comparing the contents of initrd.img-6.10.6-amd64 (failing) with those of initrd.img-6.10.4-amd64 (working) in which I found firmware in 6.10.4 which was not in 6.10.6, I have now looked more carefully, and I can see nothing relevant to sound in there.
In passing, here is part of the output of lspci -k : 00:03.0 Audio device: Intel Corporation Xeon E3-1200 v3/4th Gen Core Processor HD Audio Controller (rev 06) Subsystem: CLEVO/KAPOK Computer Device 5455 Kernel driver in use: snd_hda_intel Kernel modules: snd_hda_intel which shows the details of the hardware being controlled by snd-hda_intel. Not sure that any of this helps track down what is wrong.