apt install frr frr-pythonutils is failing on ARM architectures.
When attempting to install just frr from deb.frrouting.org it attempts to install version 7.0.1-1, and not version 7.1-1, but frr-pythonutils is version 7.1-1.
The problem appears to be the same for both armhf and arm64 on all distro versions, but amd64 and i386 do not appear to have the problem.
Quentin Armitage