Thank you so much for this example. It is very clear and useful.
I will try this out on my system and see if the inconsistent behavior
is still there.
Just wondering, what is the reason you decided to use udev rule to
trigger the service, instead of a script in /etc/network/if-up.d/ or
/etc/networkd-dispatcher/?
>
> /etc/udev/rules.d/99-nftables-netdev.rules
> ----
> SUBSYSTEM=="net", KERNEL=="enp1s0f0", ACTION=="add", ENV{SYSTEMD_WANTS}+="nftables-netdev@enp1s0f0.service"
