If you are experienced in managing a GitLab CI pipeline on macOS, and you wish to volunteer for this particular task, please join the #gtk:gnome.org 10 or the #infrastructure 10 channels on Matrix, to coordinate with GLib and GTK maintainers, and with the GNOME infrastructure team. The deadline is going to be the release of GNOME 45, September 16, 2023.
https://discourse.gnome.org/t/potential-retirement-of-the-macos-ci-builder-for-glib-and-gtk/16198