Is "outcast" also plural?

Britannica, Wiktionary, Merriam-Webster, Collins, and a few other dictionaries all said the plural of "outcast" is "outcasts".

But I have seen "outcast" used plural, as in "the outcast" -- for example:

All of the outcast were waiting for a leader to return them to their former glory.

"Food and shelter for all those outcast?" he asked, doubtfully.

Is "outcast" also plural, or is that usage of "outcast" now obsolete?

Edit: I updated my examples to better reflect my question.

Edit 2: So, @tchrist, you're saying that as an ADJECTIVE "the outcast" is grammatically acceptable to mean "the group of outcasts"?

Any adjective can always be used in a subject governing a plural verb when the unwritten noun modified by that adjective is itself plural. Usually that unwritten noun works out to something like people or things or sometimes ones, but whatever it is this noun is already recoverable in context.

Imagine a sentence like The poor are always desperate or The outcast have no course. These are adjectives, not nouns, and these subjects have no noun in them at all once the obvious bit has been left out. So it works out to The ADJECTIVE people where you skip people because it’s obvious in contect.

The Cambridge Grammar of the English Language has invented the term fused-modifier head for these constructions, but other analyses use their own terms to describe these.

The plural of An/The outcast is is (Some/The) Outcasts are. Notice that that is a noun because it inflected into the plural. But that is NOT what is happening with your example sentence. You just have a fused-modifier here where the recoverable noun is itself plural. Your adjective is just an adjective, and it cannot have number in English.