Is (a) a linking verb? :)

No, "a" is an article, not a verb at all.

Read carefully:
https://www.englishgrammar101.com/module-3/verbs/lesson-3/linking-verbs

No. A is an article and used as an adjective.

Common linking verbs are
am, is, are, was, were, become, seem

Examples:

I AM Ms. Sue.
You ARE pretty.
They WERE late.
She SEEMS tired.

To determine if "(a)" is a linking verb, we first need to understand what a linking verb is. A linking verb, also known as a copula, connects the subject of a sentence to a subject complement or an adjective that describes or modifies the subject. Common linking verbs include "is," "was," "become," "seem," "feel," and "appear."

In the case of "(a)," it appears to be a single letter rather than a word. Linking verbs are typically words, not individual letters or symbols. Therefore, "(a)" is not a linking verb.

To further analyze a word or phrase as a linking verb, you can use context clues within a sentence, such as looking for a subject complement or adjective that follows the verb. Additionally, consulting a dictionary or grammar resource can provide more information on specific verbs and their functions.