Luggae is a considered a singular subject. It will be followed by a Singular verb. 'Is'.
No, luggage can be both singular or plural. Its original meaning had to go with being something that was lugged, or hauled, up.
All the equipment has been oiled is correct. Equipment is a singular collective noun. Compare 'All the luggage has been packed', not 'All the luggage have been packed'.
The noun 'handbag' is a singular, common, compound, concrete noun; a word for a small piece of luggage used to carry money and/or personal items; a word for a thing.
"Mail" is a mass noun, so it adopts the grammar of a singular noun ("The mail is here." "Has the mail arrived yet?"), although it cannot be pluralised (1 mail, 2 mails) or combined with an indefinite article (a mail). Other examples of mass nouns are "luggage" and "advice".
luggage
Yes you can put a skateboard in a luggage that is not a carry on.
She had her luggage packed immediately. The airline lost our luggage.
Yes, you can typically leave your luggage at the hotel's luggage hold before checking in.
Its a label you attach to you luggage.
luggage works
yes it can be in your luggage