dhcpcd replacing dhclient for Trixie... or perhaps networkd?

My work on overhauling dhcpcd as the prime replacement for ISC's discontinued DHCP client is done. The package has achieved stability, both upstream and at Debian. The only remaining points are bug #1038882 to swap the Priorities of isc-dhcp-client and dhcpcd-base in the repository's override, and swaping ifupdown's search order to put dhcpcd first.

Meanwhile, ifupdown's de-facto maintainer prompted me to sollicit opinions on which of the 4 ifupdown implementations should ship with a minimal installation for Trixie. This, in turn, re-opened the debate of what should be Debian's default network configuation framework (see the thread starting with this post).

networkd

Given how most Debian ports (except for Hurd) ship with systemd, which includes a disabled networkd by standard, many people in the thread feel that this should become the default network configuration tool for minimal installations. As it happens, most of my hosts fit that scenario, so I figured that I would give another go at testing networkd on one host.

I used the following minimalistic /etc/systemd/network/dhcp.network:

[Match]
Name=en* wl*

[Network]
DHCP=yes

This correctly configured IPv4 via DHCP, with the small caveat that it doesn't update /etc/resolv.conf without installing resolvconf or systemd-resolved.

However, networkd's default IPv6 settings really are not suitable for public consumption. The key issues (see Bug #1076432):

1. Temporary addresses are not enabled by default. Worse, the setting is ignored if it was enabled by sysctl during bootup. This is a major privacy issue. Adding IPv6PrivacyExtensions=yes to the above exposed another issue: instead of using the fe80 address generated by the kernel, networkd adds a new one.
2. Networkd uses EUI64 addresses by default. This is another major privacy issue, since EUI64 addresses are forensically traceable to the interface's MAC address. Worse, the setting is ignored if stable-privacy was enabled by sysctl during bootup. To top it all, networkd does stable-privacy using systemd's time-proven brain-dead approach of reinventing the wheel: instead of merely setting the kernel's address generation mode to 3 and letting it configure the secret address, it expects the secret address to be spelled out in the systemd unit.

Conclusion: networkd works well enough for someone configuring an IPv4-only network from 20 years ago, but is utterly inadequate for IPv6 or dual-stack installations, doubly so on a software distribution that claims to care about privacy and network security.