I managed to get rid of the high-pitched beeping with a tip I first saw on LixSystems’ support page, and later on the (German) VDR portal: you make a file named /etc/modprobe.d/alsa-fix or /etc/modprobe.d/alsa-special, and into that file you put a single line containing:

    options snd-hda-intel position_fix=1 model=3stack