Are you sure it is built into manjaro as a package?
When searching I only find gnome-shell-extension-openweather-git in the AUR and the current maintainer is orphaning it. : AUR (en) - gnome-shell-extension-openweather-git
I just removed the package I had built-in my system (the one shown on the screenshot above) and now it has mysteriously disappeared completely from Pamac’s catalog and I cannot find it.
I installed the firefox add-on from https://extensions.gnome.org and then installed the extension by enabling the ON switch and clicking on the Upgrade button next to the ON switch.
GLib.FileError: Failed to open file “/usr/share/gnome-shell/extensions/openweather-extension@jenslody.de/weather-settings.ui”: No such file or directory