modules/xdgopen.nix

{
  xdg.portal = {
    enable = true;
    xdgOpenUsePortal = true;
  };
  xdg.mime = {
    defaultApplications = {
      "x-scheme-handler/http" = "firefox.desktop";
      "x-scheme-handler/https" = "firefox.desktop";
    };
  };
}