Claiming to offer a drop-in substitute all while nudging people
towards a new paradigm is not welcome.
If ifupdown's paradigm were working for people we wouldn't be having this
conversation.
[snip]
For my perspective, the main issues with ifupdown are:
1) ifupdown doesn't handle bridges and vlans without external
packages, yet it already depends upon iproute2, which provides 'ip'
i.e. a command that can handle these quite nicely.
2) ifupdown doesn't include a way to handle DHCPv6-PD for all
supported DHCP clients.
3) Since the introduction of systemd units, one can no longer rely on
interfaces being brought up sequentially following the order in which
they appear in /etc/network/interfaces.
4) That systemd unit generation blissfully ignores anything else that
physical interfaces in /etc/network/interfaces which introduces yet
more reproducibility problems.