Gmoccapy Found an error

Hmm no, I didn't have to install libgtksourceview-3.0-dev. Maybe it was installed as dependency of libgtk-3-dev?

But you are not off the hook yet because gmocappy now is the only gui that will not work on wayland with this suggestion from Seb on this issue github.com/LinuxCNC/linuxcnc/issues/2264

 Yes I have seen this and also the issues on Bookworm. But I wanted to start at the beginning

No, that one seems to be a dependency of the one I installed. 
ref:  packages.debian.org/bullseye/libgtksourceview-3.0-dev