Il s’agit ici de l’emploi pronominal impersonnel d’agir (en C)

• il s’agit de + nom ou inf. signifie il est question de (it’s about).

• il s’agit de + inf. signifie il est important de (it is important to).

Dans ton cas, il est question en effet de Drago Malefoy.

The link you provided does give the answer to that question:

il s’agit de (=c’est) – it’s a matter of, it’s
(=c’est à propos de) it’s about
Il s’agit d’une intervention bénigne. – It’s a minor operation.
de quoi s’agit-il? – What is it about?

So, there you have a translation, a proper question and an example.

Un francophone also provided il est question de and that can be also said in English: it’s a question of.

Another example

Il s’agit d’une pièce à deux personnages. – It’s a play with two people.

With own words: You can use that phrase when you want to specify the object you’re talking about more precisely. For instance: It’s an animal with eight feet.

Thus, your sentence could be translate:

It’s indeed Drago Malefoy.

Admittedly, it’s Drago Malefoy.

Said that, I wouldn’t use a question of or a matter of in your example. Both could be used in the second meaning that Un francophone said, for instance:

It’s a matter of life and death.

It’s still a matter of debate.

or in phrases like

It’s simply a question of time. (C’est juste une question de temps)

I would like to propose another translation of the expression, maybe more generic than the others. I think that in most cases, il s’agit can be translated by the expression it happens to be.

For example:

Il s’agissait en effet de Drago Malefoy.

Could be translated by:

It indeed happened to be Drago Malefoy.

It’s not really a pretty translation, but it’s somehow easy to use.

Spontaneously my mind came up with

It deals with,
It concerns,

But for direct simplicity, “it’s about” takes the biscuit! i.e. gets my vote! ( dunk, dunk, slam dunk! n’est Pas?)