I posted this in the Pi thread, but just incase:
for those using pihole if your update "breaks" and complains iproute2 is missing
check /etc/apt/sources.list and make sure it's right... mine was zero'd somehow, and iproute2 is now in backports for Debian Buster.
If you want the real tech info, I filed my findings (and suggestions) here:
... guess my username ... :P