How about just shipping a networkd.conf(.d) config snippet and .network file with the wanted defaults. This is just another instance of I-hate-systemd-for-no-reason whining
When having displaced the ISP-supplied DSL/ADSL/SDSL router at a premise using DHCP OPTIONS using a FreeBSD/Linux and ISC dhclient at many locations, and that is the client-side of DHCP.
And ISP likes to have their custom routers (which is a DHCP client, BTW) respond in all sorts of funky ISP-specific DHCP key/value sets.
> This is just another instance of I-hate-systemd-for-no-reason whining
systemd appears to (whether deliberately, or through incompetence) ignore kernel configuration and do its own thing. That's a good reason to complain, don't you think?