systemd-nspawn is actually pretty great, and is mostly just a tool that exposes functionality that systemd already needs for other reasons. IIRC it was originally developed to aid in testing systemd itself, and was initially shipped as an unsupported extra in case other people found it useful.
systemd-resolved is the only way I've ever been able to get dockerd to play nice with Tailscale DNS; it's also the best way that I've found to get a system to pick different upstream DNS servers depending on domain. The alternative is hand-rolling it with dnsmasq or something similar.
I admit I haven't really seen a huge advantage to using systemd-networkd over NetworkManager yet, but for servers with relatively static network configurations, I greatly prefer systemd-networkd over any of the various implementations of ifupdown.
> I admit I haven't really seen a huge advantage to using systemd-networkd over NetworkManager yet
I don't think there is one. systemd-networkd is explicitly not for dynamic environments like personal laptops or workstations; it has a scope and NetworkManager is largely outside it.
systemd-resolved is the only way I've ever been able to get dockerd to play nice with Tailscale DNS; it's also the best way that I've found to get a system to pick different upstream DNS servers depending on domain. The alternative is hand-rolling it with dnsmasq or something similar.
I admit I haven't really seen a huge advantage to using systemd-networkd over NetworkManager yet, but for servers with relatively static network configurations, I greatly prefer systemd-networkd over any of the various implementations of ifupdown.