Additional info: the above problem is affecting geary-mobile only. standard geary doesn't suffer from this
another EDIT: uninstalling geary-mobile -> installing standard geary -> configuring account via standard geary -> uninstalling standard geary -> installing geary-mobile does the trick, since apparently settings are shared, meaning that after this, when launched the geary-mobile, my account enabled via standard geary was already available
another EDIT: uninstalling geary-mobile -> installing standard geary -> configuring account via standard geary -> uninstalling standard geary -> installing geary-mobile does the trick, since apparently settings are shared, meaning that after this, when launched the geary-mobile, my account enabled via standard geary was already available