i'm surprised you haven't dealt with zeromq, because nix why-depends says systemd depends on it :

» nix why-depends --derivation nixpkgs#systemd nixpkgs#zeromq
/nix/store/mmxfq68bslpjqki0f7svg31cjv2pnr36-systemd-255.2.drv
└───/nix/store/js89ydnz71fv1kqgn69mm7yqfsw61lpi-iptables-1.8.10.drv
    └───/nix/store/5b85c19psp7km2mvnlwzs0gml93v289x-libpcap-1.10.4.drv
        └───/nix/store/rpgg2wwh745g9y928wb6a2w1gn23g9y1-libnl-3.8.0.drv
            └───/nix/store/hks3p38b5vdjkncdkkrcwjjqlhg1cbs7-graphviz-10.0.1.drv
                └───/nix/store/s5pcbnaqw75bxbyk3hyb2kmjr0b1viab-fontconfig-2.15.0.drv
                    └───/nix/store/q124gz30q037qq5n6vnym3n2gkf6r4n9-dejavu-fonts-minimal-2.37.drv
                        └───/nix/store/rngadqxkfwizz368b9zg3az9ifdgfgsn-dejavu-fonts-full-2.37.drv
                            └───/nix/store/rhw4k7zqgrvw36rz6cq5m6p12afpwc7l-fontforge-20230101.drv
                                └───/nix/store/ir6k22cspdsw25l4jskfrlmymhyr30g5-zeromq-4.3.5.drv

Why? Is there something wrong with zeromq on RISC-V?

I don't seem to have a fix for it and my full system rebuild is complete, so it should work fine.