Using Firefox on Ubuntu is causing problems for those users that have Firefox installed with `apt install` or have the Firefox Developer Edition. This problem doesn’t allow users to open the extension properly, opening a blank screen popup and being closed almost instantly.
This problem is generated due to an update in Gnome and the inputs of type password. The solution for this issue is simply changing the Keyboard Input method that is by default Ibus, to XIM, that is installed by default with Ubuntu.
When this is changed, just restart your computer and then all MetaMax Firefox versions should work normally.
Please Note: Changing this setting will not work if your primary language on Ubuntu is Japanese, Chinese, Korean or Vietnamese.