I have been with the Rpi people for 2 days working on this sound issue that really has been going on for 2 months with the newer kernels and now has crept into 5.10. Today they pushed the fix.
https://github.com/raspberrypi/linux/issues/4634
Long story short I am compiling a new 5.10 kernel with the fix which I will push when it is done so upgrade when I get it pushed and the mirrors sync. It will be pushed to all branches.
I do not think it affects you but this new kernel will install a new cmdline.txt and back up the old one so if some one else has some custom configs in it they can refer to the backup and add back to the new cmdline.txt as long as snd-bcm2835.enable_compat_alsa=whatever & snd_bcm2835.enable_headphones=1 is not added back.
I hate to mess with someone’s custom config’s but I am trying to avoid another firestorm over this yet again needed config changes and be compatible with the new images that were released yesterday because some do not like to search/read the forum before they post an issue.
linux-rpi4 5.10.73-3
linux-rpi4-headers 5.10.73-3
ADDED:
New 5.10.73-3 kernel now in all branches when the mirrors sync.