SOLVED by #2.
Standard CE PVE install (3 months old - currently v7.1-10) - This morning my usual apt upgrade failed with below snippet.
dpkg-deb (subprocess): decompressing archive '/var/cache/apt/archives/pve-qemu-kvm_6.1.1-2_amd64.deb' (size=26425464) member 'data.tar': lzma error...
