Figured out that I don't need a special screen, just send events to the component directly with OnEvent. However, you have to component->Add() or call Render(component, []) with it or else it's not considered a child.

panel.hpp

@@ -6,7 +6,6 @@
 #include <ftxui/dom/canvas.hpp>
 #include <ftxui/screen/screen.hpp>
 #include <ftxui/dom/canvas.hpp>
-#include "sfml_screen.hpp"  // for SFMLScreen
 #include <locale>
 #include <codecvt>
 
@@ -20,7 +19,7 @@ struct Panel {
   std::wstring $screenout;
   bool $dirty = true;
   Component $component;
-  SFMLScreen $screen;
+  Screen $screen;
   bool $must_clear = true;
   std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>> $converter;
 
@@ -29,12 +28,14 @@ struct Panel {
     y(y),
     width(width),
     height(height),
-    $screen(SFMLScreen::FixedSize(width, height)),
+    $screen(Screen(width, height)),
     $must_clear(must_clear)
-  {};
+  {
+  };
 
   void resize(int width, int height);
-  void set_renderer(std::function< Element()> render);
+  void set_renderer(Component renderer);
+  void add(Component child);
   void render();
   const std::wstring &to_string();
   const Screen &screen();