This bug has already been reported to upstream via https://linuxonly.ru/forum/modem-manager-gui/57/cannot-load-modem-manager-gui-arch-linux-lts-i3wm/#post-241
- Bug#922608: modem-manager-gui aborts to start after modemmanager ... Persmule
- Bug#922608: Acknowledgement (modem-manager-gui aborts to sta... persmule
- Bug#922608: Info received (Bug#922608: Acknowledgement (mode... Persmule