It looks that Framebuffer got out of sync with CtrlCore.h and gcc spits out plenty of 'no member declared' errors.
It complains about functions that ends with 0 (WndUpdate0r, EventLoop0, GuiSleep0, WndShow0 etc.)
Can I simply remove all those 0s from function names or maybe they should be wrapped by functions without 0 in names?

In file included from /home/zbych/upp.out/reference/Framebuffer/GCC.Debug.Debug_Full.Gui.Linuxfb.Shared/$blitz.cpp:37:0:
/home/zbych/upp/reference/Framebuffer/Wnd.cpp:135:5: error: prototype for 'int Upp::Ctrl::RegisterSystemHotKey(Upp::dword, Upp::Callback)' does not match any in class 'Upp::Ctrl'
 int Ctrl::RegisterSystemHotKey(dword key, Callback cb)
     ^~~~
In file included from /home/zbych/upp/reference/Framebuffer/Draw.cpp:1:0,
                 from /home/zbych/upp.out/reference/Framebuffer/GCC.Debug.Debug_Full.Gui.Linuxfb.Shared/$blitz.cpp:3:
/home/zbych/upp/uppsrc/CtrlCore/CtrlCore.h:793:17: error: candidate is: static int Upp::Ctrl::RegisterSystemHotKey(Upp::dword, Upp::Function<void()>)
  static  int    RegisterSystemHotKey(dword key, Function<void ()> cb);
                 ^~~~~~~~~~~~~~~~~~~~
In file included from /home/zbych/upp.out/reference/Framebuffer/GCC.Debug.Debug_Full.Gui.Linuxfb.Shared/$blitz.cpp:37:0:
/home/zbych/upp/reference/Framebuffer/Wnd.cpp:377:37: error: no 'void Upp::Ctrl::WndUpdate0r(const Rect&)' member function declared in class 'Upp::Ctrl'
 void Ctrl::WndUpdate0r(const Rect& r)
                                     ^
/home/zbych/upp/reference/Framebuffer/Wnd.cpp:409:33: error: no 'void Upp::Ctrl::EventLoop0(Upp::Ctrl*)' member function declared in class 'Upp::Ctrl'
 void Ctrl::EventLoop0(Ctrl *ctrl)
                                 ^
/home/zbych/upp/reference/Framebuffer/Wnd.cpp:444:28: error: no 'void Upp::Ctrl::GuiSleep0(int)' member function declared in class 'Upp::Ctrl'
 void Ctrl::GuiSleep0(int ms)
                            ^
/home/zbych/upp/reference/Framebuffer/Wnd.cpp:460:27: error: no 'void Upp::Ctrl::WndShow0(bool)' member function declared in class 'Upp::Ctrl'
 void Ctrl::WndShow0(bool b)
                           ^
/home/zbych/upp/reference/Framebuffer/Wnd.cpp:465:23: error: no 'void Upp::Ctrl::WndUpdate0()' member function declared in class 'Upp::Ctrl'
 void Ctrl::WndUpdate0()
                       ^
/home/zbych/upp/reference/Framebuffer/Wnd.cpp: In member function 'void Upp::Ctrl::DestroyWnd()':
/home/zbych/upp/reference/Framebuffer/Wnd.cpp:536:16: error: 'class Upp::Ctrl' has no member named 'WndDestroy0'; did you mean 'WndDestroy'?
    topctrl[i]->WndDestroy0();
                ^~~~~~~~~~~
                WndDestroy
/home/zbych/upp/reference/Framebuffer/Wnd.cpp: At global scope:
/home/zbych/upp/reference/Framebuffer/Wnd.cpp:552:24: error: no 'void Upp::Ctrl::WndDestroy0()' member function declared in class 'Upp::Ctrl'
 void Ctrl::WndDestroy0()
                        ^
/home/zbych/upp/reference/Framebuffer/Wnd.cpp:576:30: error: no 'void Upp::Ctrl::SetWndForeground0()' member function declared in class 'Upp::Ctrl'
 void Ctrl::SetWndForeground0()
                              ^
/home/zbych/upp/reference/Framebuffer/Wnd.cpp:602:30: error: no 'void Upp::Ctrl::WndEnable0(bool*)' member function declared in class 'Upp::Ctrl'
 void Ctrl::WndEnable0(bool *b)
                              ^
/home/zbych/upp/reference/Framebuffer/Wnd.cpp:608:32: error: no 'void Upp::Ctrl::SetWndFocus0(bool*)' member function declared in class 'Upp::Ctrl'
 void Ctrl::SetWndFocus0(bool *b)
                                ^
/home/zbych/upp/reference/Framebuffer/Wnd.cpp:650:39: error: no 'void Upp::Ctrl::WndSetPos0(const Rect&)' member function declared in class 'Upp::Ctrl'
 void Ctrl::WndSetPos0(const Rect& rect)
                                       ^
/home/zbych/upp/reference/Framebuffer/Wnd.cpp:661:57: error: no 'void Upp::Ctrl::WndScrollView0(const Rect&, int, int)' member function declared in class 'Upp::Ctrl'
 void  Ctrl::WndScrollView0(const Rect& r, int dx, int dy)
                                                         ^
In file included from /home/zbych/upp.out/reference/Framebuffer/GCC.Debug.Debug_Full.Gui.Linuxfb.Shared/$blitz.cpp:70:0:
/home/zbych/upp/reference/Framebuffer/Top.cpp: In member function 'void Upp::TopWindow::SyncSizeHints()':
/home/zbych/upp/reference/Framebuffer/Top.cpp:27:2: error: 'SyncCaption0' was not declared in this scope
  SyncCaption0();
  ^~~~~~~~~~~~
/home/zbych/upp/reference/Framebuffer/Top.cpp:27:2: note: suggested alternative: 'SyncCaption'
  SyncCaption0();
  ^~~~~~~~~~~~
  SyncCaption
/home/zbych/upp/reference/Framebuffer/Top.cpp: At global scope:
/home/zbych/upp/reference/Framebuffer/Top.cpp:30:28: error: no 'void Upp::TopWindow::SyncTitle0()' member function declared in class 'Upp::TopWindow'
 void TopWindow::SyncTitle0()
                            ^
/home/zbych/upp/reference/Framebuffer/Top.cpp:35:30: error: no 'void Upp::TopWindow::SyncCaption0()' member function declared in class 'Upp::TopWindow'
 void TopWindow::SyncCaption0()
                              ^
/home/zbych/upp/reference/Framebuffer/Top.cpp: In member function 'virtual void Upp::TopWindow::State(int)':
/home/zbych/upp/reference/Framebuffer/Top.cpp:52:2: error: 'SyncCaption0' was not declared in this scope
  SyncCaption0();
  ^~~~~~~~~~~~
/home/zbych/upp/reference/Framebuffer/Top.cpp:52:2: note: suggested alternative: 'SyncCaption'
  SyncCaption0();
  ^~~~~~~~~~~~
  SyncCaption
/home/zbych/upp/reference/Framebuffer/Top.cpp: In member function 'void Upp::TopWindow::Open(Upp::Ctrl*)':
/home/zbych/upp/reference/Framebuffer/Top.cpp:84:2: error: 'SyncCaption0' was not declared in this scope
  SyncCaption0();
  ^~~~~~~~~~~~
/home/zbych/upp/reference/Framebuffer/Top.cpp:84:2: note: suggested alternative: 'SyncCaption'
  SyncCaption0();
  ^~~~~~~~~~~~
  SyncCaption

It is kind of deprecated and was never 'canonical' anyway.
Perhaps you could give a try to VirtualGui instead?
Mirek

uses
	Painter,
	CtrlLib,
	GLDraw,
^^^^^^^^^^^^^^^^^^^^^^
	PdfDraw;

library(POSIX) "SDL2 SDL2main GL";
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
library(WIN32) "SDL2.lib SDL2main.lib OpenGL32.lib";
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

I have one more question regarding translation of key (up/down) events.
How should I know when to send some key press as ascii value and when as K_* value?
For example when I call Ctrl::DoKeyFB with key 'a' as ascii code it is shown in Uword editor, but Ctrl+a won't work.
When I translate key 'a' to K_A, Ctrl+a works, but letter 'a' won't show in the editor.
Maybe I should call Ctrl::DoKeyFB twice? One call with ascii code and second one with K_* value?

In the SDL backend there are two separated paths SDL_TEXTINPUT and SDL_KEYDOWN/SDL_KEYUP in HandleSDLEvent.
But from libinput I receive just key up/down events