How to conditionally avoid Gtkmm 4?

GNU emacs 32 is able (on Linux) to conditionally use GTK, that is to avoid using GTK (and XOpenDisplay) with its -nw program option.

I am coding on github.com/RefPerSys an open source program (inference engine in C++), and I would like it to use gtkmm-4.0 conditionally: with some program option it should avoid having any graphical interface, with some other program option it would use Gtkmm-4.0

Any hints or advices or open source examples in C++ are welcome

Regards.

NB: see same question in French