PyGObject cannot be built in a manylinux environment
Commit 551a770a bumped the minimum GLib version to 2.64, with the rationale that this is the version provided by Debian Bullseye and Ubuntu 20.04.
However, the most recent manylinux image (manylinux_2_28) is based on AlmaLinux 8, which only provides Glib 2.56.4.
While I definitely understand the desire to bump the minimum versions, and the need to deprecate old releases, manylinux is as close as the Linux community gets to a standardised binary base image. This deprecation/version bump means there is no standardised linux environment in which the Python bindings to GObject can be compiled.
Personal preference would be to revert this version bump to retain compatibility with manylinux; but at the very least the Glib minimum version and/or broad Linux version compatibility policy should be more prominently advertised.