Can an adverb be a noun?

I have seen this post for the answer to my question, but this is not much help in case of the question I am going to ask.

Here is an example sentence -

The new design of Twitter profile is more of a Facebook profile than never before.

than here is a preposition, there is no doubt about that. But before after than acts like a noun. But from dictionary entry against before doesn't say it's a noun.

So what is the explanation?

'[T]han here is a preposition, there is no doubt about that.' [OP]

and

'A noun is the only part of speech possible after a preposition'

and

In the accepted phrase 'better than ever before', 'ever' cannot be a noun.

So we have a contradiction. The only question to address really is how many of the above assertions are not true?

If we look at

'It is better than [it] ever [was before]

we find a construction which presents no problems. Here, 'than' is a conjunction; there is no doubt about that. 'Ever' is an adverb.

But in the ellipted version, 'than' is now an ex-conjunction and 'ever' is an ex-adverb. In other words, forcing traditional analyses on elliptical structures will lead to extra-grammatical analyses (ie 'the rules' will be broken).

To prate or not to prate? That is the scortle.

You’ve asked a loaded question when you say, “Can an adverb be noun?” It has hidden assumptions that render both potential answers — that is, either yes or no — in some way wrong.

It’s like asking someone whether they’ve stopped beating their husband yet. No matter whether they answer yes or no, they’ve landed themselves in hot water.

In the husband-beating question, the problems should I hope be self-evident. In yours, let me spell them out for you.

You are assuming that a word in isolation “is” some part of speech. This is never true. Parts of speech and other, broader labels (such as subject, predicate, verbal phrase, adverbial phrase, direct object, &c) are applied to constituents of a phrase or larger utterance once it has been subjected to syntactic analysis — once it has been parsed.

A single word in complete isolation has no part of speech. It cannot. Only when you deduce or infer what role that word is playing in the larger syntactic context can one begin to assign such labels.

For example, what part of speech is each of these words:

floop
flump
plock
prate
rast
ruzz
ruzzle
rynt
scortle
tyrn

Kinda tough, right? Would these additions make it any easier?

derasted
flooped
floopess
floops
flumper
flumpette’s
nyrt’s
plockest
prated
pratess
pratest
rastest
rastfully
ruzzest
ruzzled
scortle’s

The answer is yes, it helps considerably — but not completely. That’s because what you really need to complete the job is this:

My scortle’s floopess prated me to rastfully flump her the ruzzest plock I could tyrn.

Or perhaps this:

My nyrt’s pratess flooped me to ruzz her the plockest flumper I could scortle the rastest.

Or maybe even this:

My flumpette’s scortle ruzzled me to pratefully plock her the most derasted of floops I could rynt.

I trust you will now have no trouble assigning parts of speech to all of floop, floops, flooped, floopess, flump, flumper, flumpette’s, nyrt’s, plock, plockest, prated, pratess, pratest, ruzz, ruzzest, ruzzled, rynt, scortle, scortle’s, and tyrn.

The flumpette’s rast floop

Or will you?

You see, without having the sentences, you can have no part of speech. And even once you have the sentences, the part-of-speech tag assigned a lexical item in one sentence quite often contradicts the POS assignment in another sentence.

So you see, it makes no sense to ask whether an adverb can be noun. It cannot be, because it is an adverb. That does not mean that a word that is sometimes used as an adverb cannot turn around the next floop and get itself used as noun this time around.

A good example of that is today, tomorrow, and yesterday. Today I have nothing to do, but tomorrow I shall rue the yesterday that I shall by then have squandered. Or, as a better writer than I once said:

She should have died hereafter.
There would have been a time for such a word.
Tomorrow, and tomorrow, and tomorrow,
Creeps in this petty pace from day to day
To the last syllable of recorded time,
And all our yesterdays have lighted fools
The way to dusty death. Out, out, brief candle!
Life’s but a walking shadow, a poor player
That struts and frets his hour upon the stage
And then is heard no more. It is a tale
Told by an idiot, full of sound and fury,
Signifying nothing.

So whether you classify a word as this or that, it signifies nothing in isolation.

Partes orationis quot sunt?

This is true for Donatus’s eight classical parts of speech, from

Partes orationis quot sunt? Octo. Quae?

nomen

pronomen

verbum

adverbium

participium

coniunctio

praepositio

interiectio

To the modern analyst’s standard workhorses:

articles
quantifiers
determiners
adjectives
numbers
nouns
pronouns
clitics
verbs
proverbs
adverbs
circumpositions
conjunctions
contractions
expletives
interjections
negators
particles
prepositions
postpositions

To the subdivider’s nuanced list of:

demonstrative adjectives
zero article
definite articles
indefinite articles
partitive articles
correlative conjunctions
coördinating conjunctions
subordinating conjunctions
count nouns
mass nouns
proper nouns
cardinal numbers
direction particles
locative particles
demonstrative pronouns
demonstrative pronouns
emphatic pronouns
impersonal pronouns
indefinite pronouns
interrogative pronouns
locative pronouns
personal pronouns
possessive pronouns
reciprocal pronouns
reflexive pronouns
relative pronouns
possessive terminers
auxiliary verbs
bitransitive verbs
copular verbs
intransitive verbs
modal verbs
transitive verbs

Because no matter what set you pick — and there are many others besides just these three — when you try to talk about them in the abstract and apply them to a single word in isolation, they are all so much sound and fury, signifying nothing.