dev-python/pygobject-3.28.2 works fine, but dev-python/pygobject-3.29.1 does not install anything useful, which causes revdeps (gedit, totem, networkmanager, etc.) to fail like this :
configure: error: Package requirements (pygobject-3.0 >= 3.0.0) were not met:
No package 'pygobject-3.0' found
I suggest using their GitHub issues for reporting issues in that overlay.
This one appears to be this:
PS: gnome-next overlay has no relation to Gentoo GNOME team
> PS: gnome-next overlay has no relation to Gentoo GNOME team
My mistake. I thought gnome-next was provided by one of the Gentoo devs.