Merge pull request #146709 from Artturin/underscorename

nixos/modules/tasks/network-interfaces.nix

···
         network node hostname (uname --nodename) the option
         boot.kernel.sysctl."kernel.hostname" can be used as a workaround (but
         the 64 character limit still applies).
+
+        WARNING: Do not use underscores (_) or you may run into unexpected issues.
       '';
+       # warning until the issues in https://github.com/NixOS/nixpkgs/pull/138978
+       # are resolved
     };
 
     networking.fqdn = mkOption {