Could you please provide an example of an adverb following a linking verb. I thought primarily adjectives and nouns followed linking verbs.
Something is not right there:
'The next meeting will be on the fifth of February.' Here we have an existential statement, an intransitive use of 'be' not a linking verb. If you consider the adverbial 'on the fifth of February' to be a description of 'The next meeting' a lá 'The next meeting will be long.' try to substitute 'seem':
The next meeting will seem long. 'seem' linking verb
*The next meeting will seem on the fifth of February. Not good.
The next meeting will take place on the fifth of February. transitive 'take'
The next meeting, on the fifth of February, will be. Master Yoda speak!
The next meeting, on the fifth of February, will be on the fifth floor. 'be' a locative verb.
The next meeting, on the fifth of February, on the fifth floor, will be the fifth this year. 'be' linking verb
The meeting is the fifth this year.
Isn't here a location? How can 'he' be a location? He can be 'in' a location: He is in London.
He is an engineer, linking verb, apposition
He is happy. linking verb, state adjective.
He is here. locative verb *A here-ish him. cf Happy me!
Why do you suppose 'be' is and only is copular?
In 'He is here.' I equate it directly with Spanish 'estar' = be in a place, OE 'eom' = remain (in) OE wesan = remain. The forms of 'be' are a mixture of the paradigms of three old verbs, two of which meant 'remain' How can you couple/equate a person with a place? A person can only 'be in' a place, a location.
The verb 'be' can, in fact, function both as a copular full verb (in which capacity it may be complemented by a variety of forms, including noun phrases, adjectives, adverbials and infinitives) and as an auxiliary verb (as in I am reading).
You will not fail to infer from this that an English copula is not automatically restricted - as you appear to think it ought to be - to the assertion of some kind of 'identity' between subject and complement, the functionality of 'be' as a copula in the sentence in question being therefore not a matter of opinion, speculation or supposition, but a simple taxonomic fact accepted by any competent grammarian of the English language.
As for your interesting observations about Spanish grammar (which, unlike English, possesses two distinct verbs corresponding to English 'be'), I suggest you reserve them for questions relating to that particular language!
I think it is fairly clear, though, from the subsequent statement that reference was, in fact, to adverbial complementation of a copula.
(If not, Pedroski and I have been completely wasting our time!)