Hmm ... It's impossible ;-) This RPM doesn't exist on any FTP server

Provides :
gtkmm30-devel
gtkmm30-devel(x86-32)
pkgconfig(gdkmm-3.0)
pkgconfig(gtkmm-3.0)

Requires :

/usr/bin/pkg-config
gtkmm30(x86-32) = 3.22.2-3.el8
libgdkmm-3.0.so.1
libgtkmm-3.0.so.1
pkgconfig(atkmm-1.6) >= 2.24.2
pkgconfig(cairomm-1.0) >= 1.12.0
pkgconfig(gdk-pixbuf-2.0) >= 2.35.5
pkgconfig(gdkmm-3.0)
pkgconfig(giomm-2.4) >= 2.49.1
pkgconfig(gtk+-3.0) >= 3.22.0
pkgconfig(gtk+-unix-print-3.0)
pkgconfig(pangomm-1.4) >= 2.38.2
rpmlib(CompressedFileNames) <= 3.0.4-1
rpmlib(FileDigests) <= 4.6.0-1
rpmlib(PayloadFilesHavePrefix) <= 4.0-1
rpmlib(PayloadIsXz) <= 5.2-1

Content of RPM :
/usr/include/gdkmm-3.0
/usr/include/gdkmm-3.0/gdkmm
/usr/include/gdkmm-3.0/gdkmm.h
/usr/include/gdkmm-3.0/gdkmm/applaunchcontext.h
/usr/include/gdkmm-3.0/gdkmm/color.h
/usr/include/gdkmm-3.0/gdkmm/cursor.h
/usr/include/gdkmm-3.0/gdkmm/device.h
/usr/include/gdkmm-3.0/gdkmm/devicemanager.h
/usr/include/gdkmm-3.0/gdkmm/display.h
/usr/include/gdkmm-3.0/gdkmm/displaymanager.h
/usr/include/gdkmm-3.0/gdkmm/dragcontext.h
/usr/include/gdkmm-3.0/gdkmm/drawingcontext.h
/usr/include/gdkmm-3.0/gdkmm/event.h
/usr/include/gdkmm-3.0/gdkmm/general.h
/usr/include/gdkmm-3.0/gdkmm/glcontext.h
/usr/include/gdkmm-3.0/gdkmm/monitor.h
/usr/include/gdkmm-3.0/gdkmm/pixbuf.h
/usr/include/gdkmm-3.0/gdkmm/pixbufanimation.h
/usr/include/gdkmm-3.0/gdkmm/pixbufanimationiter.h
/usr/include/gdkmm-3.0/gdkmm/pixbufformat.h
/usr/include/gdkmm-3.0/gdkmm/pixbufloader.h
/usr/include/gdkmm-3.0/gdkmm/private
/usr/include/gdkmm-3.0/gdkmm/private/applaunchcontext_p.h
/usr/include/gdkmm-3.0/gdkmm/private/color_p.h
/usr/include/gdkmm-3.0/gdkmm/private/cursor_p.h
/usr/include/gdkmm-3.0/gdkmm/private/device_p.h
/usr/include/gdkmm-3.0/gdkmm/private/devicemanager_p.h
/usr/include/gdkmm-3.0/gdkmm/private/display_p.h
/usr/include/gdkmm-3.0/gdkmm/private/displaymanager_p.h
/usr/include/gdkmm-3.0/gdkmm/private/dragcontext_p.h
There is 530 files more in these RPM.