Feryno allows me to port his Fdbg (http://fdbg.x86asm.net/ or http://feryno.host.sk/)
I used his Fdbg to create a UEFI application, but porting a complex debugger without a debugger seems very hard for a newbie.
I could try to run Menuet in Bochs, but also that is new for me. Does anyone else tried this before?.

It would be nice to optionally display debug output on a second monitor (on a system with support for multiple monitors).
But I have no clue on how to configure this, or to obtain the framebuffer address.
UEFI firmware intentionally does not pass that information to a boot loader (an advice from Intel).
Maybe the Bios or MenuetOs can. I appreciate help and/or feedback.