valent

Note that you have to open firewall ports for other devices to connect to it. Use either:

programs.kdeconnect = {
  enable = true;
  package = pkgs.valent;
}

or open corresponding firewall ports directly:

networking.firewall = rec {
  allowedTCPPortRanges = [ { from = 1714; to = 1764; } ];
  allowedUDPPortRanges = allowedTCPPortRanges;
}