That was "fun". It seems that #starfive's linux-headers .deb package for their kernels is compressed with zstd rather than gz/xz which is not supported by the version of dpkg shipped with their own Debian bookworm image on #RISCV.
Fortunately you can extract the downloaded .deb, recompress the files and create a new .deb:
ar -m -c -a sdsd linux-headers-6.6.20-starfive_6.6.20-vf2-1SF_riscv64.deb debian-binary control.tar.xz data.tar.xz
then install them with "dpkg -i"
https://github.com/yktoo/indicator-sound-switcher/issues/113#issuecomment-997810115